Preface

The first chapter of Genesis, the Elohist account of the creation, can be read in many ways and seen through different eyes. To some it is a poetic abridgement of tribal stories, full of flowery imagination and touching naiveté, to others it is the divine words of eternal wisdom received by Moses on the mountaintop. What is it to me? Most often I think about it as a remarkably accurate, succinct rendition of the history of our planet that is given in simple language accessible to anyone from a scientist living today to a nomad living thousands of years ago. Above all, it the story of beginnings and as such, it has uncanny spell over me. There is no other book like it, nor there ever be another book like it. There are thousands of creation myths; if the book of Genesis is such a myth, it clearly stands apart. But is it a myth?

I am not sure at all that it is such a myth. This view rests on the assumption that this book looks backwards into the past in order to explain the present. It can indeed be read like that, but it can also be read as the story about the future – our future. If the purpose of our cameo appearance in this world is to know ourselves, as we are told by many a sage, we can never fulfill this high purpose and learn about who we are until we understand how our world was created, and we will never reach this understanding unless we ourselves create a world. The book of Genesis can be read as an instruction book passed to us from the time immemorial about how to create a habitable world in which creatures like us are not only remote possibility but the striking actuality. Following this line of reasoning, one can ask many questions that give new perspective to the creation story. Suppose you have this grand goal in mind – how to bring it about? What choices should be made? What requirements should be met? What is to be expected during the execution of this plan? This is not the perspective of a creature. This is the perspective of the creator. Unless we adopt this perspective and follow it to its logical end, our own past will never open to us fully. Our knowledge is wholly inadequate to get more than a glimpse of such a perspective, and this glimpse is a distorted reflection of a reflection, but even such faulty and foggy visage already brings the appreciation of the creation that is difficult to obtain otherwise. One begins to see what this planet went through in a new way and recognize better why its journey was along this tortuous and dangerous path. The book of Genesis is the book of the past, the present, and the future.

Yet another reading of this book can be achieved simply by placing the question “why” before each verse. Why are there heaven and earth? Why were the waters parted? Why is there land? Do you know why? Have you asked yourself why? Are we any closer to satisfying answers to these “whys” than supposedly “naïve” and ignorant people living three millenia ago when the book was codified? What good are our science and our knowledge if we cannot answer such simple, naïve, childish questions? – and we cannot, I can assure you of that. That is because such questions are, in fact, among the hardest questions one can ask, and that is the chief reason why people go to extreme length to avoid asking and answering such questions. Answering these questions is the end point of science and all of our knowledge. It is the litmus paper, the ultimate test of one’s own knowledge and the command of this knowledge, of one’s imagination, of one’s rationality, of one’s inspiration. The book of Genesis is not only the book of answers, but it is also the book of questions that will always be with us. It is a problem book.

Speaking of questions, the first question that occupies my mind every time I read the book of Genesis is, why is this story so true and accurate in detail? Why are the best educated guesses supplied by the scientific age (all of which derivative of the story told in the Genesis) read more like the notes on its margins rather than its cardinal revision? Would we be willing to write these notes at all, had we not had this story as the foundation of our civilization? Our ingenious theories fill in much detail, lots of detail indeed, but these theories leave the pivotal events and the overall structure of the narrative intact. Why is that so? If this book is a collection of fantastic yarns and ancient myths, as we are constantly reminded, why do these make-up stories have such a hold on us? Why other like stories do not? Brushing this question away with an involved historical retrospective on the composition of the Bible does not begin to address this question. Written or oral, all stories begin somewhere. Where did this story begin? Does it come from the same source where all our truths and insights originate, the one that we call intuition and inspiration? And if that is so, does it matter how this inspired vision found its way into the written text passed to us from the depth of time? This story is too intricately involved into making us what we are to declare it a tall tale. It totally permeates our culture and informs our entire way of thinking about the world, even and especially the thinking of those thinkers who adamantly refuse to take it on faith. It is this kind of a story. The book of Genesis is the truth that defines us.

Finally, it is a story of the creation of the world in which the unit of the creation is a day. Could it really be true that this world in its entire variety and splendor has been created in a few days? The uncomfortable truth is that it is indeed so. The seven days of creation have been dispersed through the vastness of time measured by billions of years, but the improbably rare – miraculous - acts that occurred on these momentous days is what shaped our world to a much greater extent than the countless days in between. Our land begins at the instant of the glancing collision of the young Earth with another planet that gave us the Moon. Our water begins on the fateful day when prokaryotic Life arrived on this planet. The animals begin on the all-important day two billion years ago when two bacteria stepped on the thorny road towards individual existence. The entire natural history can be viewed as the sequence of a few days on which the nearly impossible happened; without these few days it would be different history. Whether we call such defining moments chance or miraculous acts of creation is semantic unimportance, because we do not know what chance is. The book of Genesis is the book of one-day miracles that did happen.

It is in this mindset that I embarked on retelling this book. My knowledge is limited and my talents are few for such an enterprise, and what comes out frustrates and disappoints me. I cannot do justice to this book and tell the story well. But I am not doing it for myself and for my own satisfaction. I first heard this story as a little boy, from my father who read it to me aloud. I was fascinated by the story and barraged my poor father with endless questions – and he spared no effort trying to answer these questions as best as he could. Now I have a little boy of my own, and owe him what I was fortunate to receive myself: one person’s vision of the first chapter of the most important book ever written. I cannot ask my father to do that for my child because my father is no longer alive. And yet he is still talking to you – this time, through me. And it is not only him – my father heard this story from his mother and she heard it from her father, and so on. I cannot break this chain. The story has to go on, as its place is not inside a dusty book, its place is in our hearts and thoughts; it has to be retold, it must be retold. Our children are waiting for their answers.

So, let the story begin.

In the Beginning...

Why is there land?

...And God said, Let the waters under the heaven be gathered together unto one place, and let the dry land appear: and it was so. And God called the dry land Earth; and the gathering together of the waters called the Seas: and God saw that it was good. Gen. 1:9-10

Why do we have land? The face of our planet could have been quite different from the familiar one, with the division into spatious seas and continents: it could have been one vast superocean with the occasional volcanic archipelago. I do not think that there is any settled answer to this question, and I am not alone in believing so. Retospectively, the division of the surface into the sea and the land was "good," - it was pre-requisite for the later important developments - but how this good came about?

...Numerical experiments show that the thermal boundary layer of the Earth, the lithosphere, controls mantle convection today. We now understand that the sinking of dense lithosphere in subduction zones is responsible for plate motions and seafloor spreading and is the principal way that Earth cools. The hotter early Earth may have had a weaker and less dense lithosphere and so had a different style of mantle convection. Understanding when and why plate tectonics began is one of the most important unresolved problems in our understanding of the Earth. http://www.utdallas.edu/~rjstern/PlateTectonicsStart/presentations.htm

Wegener's 1915 treatise on plate tectonics was called "The Origin of Continents and Oceans." Today, Wegener's theory is the foundation of geology despite the inconvenient truth that the mechanism for plate tectonics remains poorly understood. Do we actually know the answer to his original question? The typical answer one gets is that the continental plates are moved around by tectonism, but this does not explain how the plates themselves have formed. The plate tectonics started about 2-2.5 Gya, which is pretty late in the game, and what started it remains a mystery. The prevailing opinion is that the motion of the cratons began when the upper mantle cooled. Then water started to get into the mantle by subduction and that reduced friction allowing plate tectonics. Another theory I heard is that plate tectonics might have required Life: the subduction of carbonate sediments made the mantle less viscous, lubricating the motion. Before photosynthesis kicked in, the calcification was inefficient and water was acidic. Both of these answers suggest that plate tectonics is the indicator of habitability of the planet. Most of the accounts of Archean geology leave the problem out, yet suggest very different Earth from the one we know:

...The active tectonics of the Archean produced numerous, relatively small landmasses that were very mobile as they floated on the turbulent mantle. Toward the end of the Archean, however, these minicontinents had begun to coalesce. By about 2.5 Gya when the Archean eon came to an end a more tectonically stable supercontinent had formed from the accreted landmasses. About 70% of modern continents are Archean in age and were derived from this single large landmass. This supercontinent had a much thicker crust than the earlier, smaller crusts and heat flow from the mantle had begun to subside. As a result volcanic and tectonic activity within and along the margins of the supercontinent, were reduced significantly by the start of the Proterozoic.
http://www.bookrags.com/research/archean-woes-01

...The interior of the Archean Earth was probably about 3 times hotter than it was today because of the greater concentration of radioactive isotopes and the residual heat from the Earth's accretion. The mantle was probably much more fluid and the crust much thinner, resulting in rapid formation of oceanic crust at ridges and hot spots and rapid recycling of oceanic crust at subduction zones. The Earth's surface was probably broken up into many small plates with volcanic islands and arcs in great abundance. Small protocontinents formed as crustal rock was melted and remelted by hot spots and recycled in subduction zones. By the end of the Archean there were significant episodes of metamorphism occurring leading to the aggregation of protocontinents and the production of large amounts of continental crust. This interval of extensive cratonization is unparalleled in Earth history - it has never been repeated - and geologists are not sure why it occurred. http://people.hofstra.edu/j_b_bennington/2cnotes/archean.html

Our present continents are the fragments of supercontinent Rodinia that formed 1.3 Gya; nobody knows what preceeded Rodinia (several earlier supercontinents have been postulated) or what caused its eventual breakup 750-900 Mya. There is also disagreement whether the budget of the continental crust remained constant throughout the Earth history. The shields (cratons) and their disassembling and re-assembling have been the fixture for a long time, and the cratons mixed little with the underlying asthenosphere, but how these cratons originated is anyone's guess. All the evidence points to very early differentiation of the mantle into regions of different chemical composition that have never been homogenized again, just shuffled and reshuffled around, although juvenile material has been added. The origin of the proto-cratons was the early and unique event in Earth's history.

There have been all kinds of speculations about this event (e.g., exotic superplumes). A few paleogeologists suggest extraterrestrial origin of these proto-cratons. Some say there was an era of massive bombardment that defined the composition of the crust without the loss of the hydrosphere. Others suggest that the event that made continents possible at a much later date was the impact that produced the Moon. The inhomogeneity that made the formation of the proto-cratons - and our land - possible was the consequence of dramatic reconstitution of the earth surface by this impact.

...The impact was at just the right angle to almost bounce off, but to be captured and swallowed by the Earth. The highly oblique impact struck a glancing blow to the Earth's surface and set up giant shock waves that spalled material into space. The debri formed a ring around the proto-Earth and then condensed into one or more glowing clumps of molten material that finally amalgamated into the Moon. When the dust settled, the nature of the Earth had been changed forever, as 60-70% of its primordial crust had been blasted off into space.

...We accept without comment that we actually have continents and oceans as distinct entities, but no other planet in our system is organised like this. Today, the Earth is about 70% ocean and 30% land. If we replace the missing 70% of crust, then we will entirely fill the ocean basins. The secret of plate tectonics is that the Earth has gaps between the continents, and so they can move around like a sliding block puzzle. But if we replace the missing crust, there are no longer any spaces to slide into. Although tectonic forces might tug and squeeze, all they can do is make a few wrinkles here an there. That's what happens on Venus, where the crust is planetwide and 30 km thick everywhere. On Venus nothing can rift, or spread, or subduct, or collide, because there's already something there blocking the way.

...If we restored the Moon to the Earth, we would block up plate tectonics. The planet would have to find other ways of losing heat - like the profuse volcanism of Venus, or the massive stacked volcanoes of Mars. Plate tectonics would stop. (Or would have never started). The oceans would flood the land, and any mountain belts would be worn away in a few hundred million years. Soon, there would be nothing left but a ball of water, with just an occasional volcanic island poking through the spindrift. The Earth is not unique because if its oceans. Any planet in the right part of the habitable zone will have those. What is unique about the Earth is that it has LAND. If the moon had not carried away most of the crust, there would be no ocean basins, no land, and no chance for life to evolve on land.
http://www.spacedaily.com/news/life-01x1.html

Could it be that the reason we have the opportunity to live on land was the nearly improbable catastrophic collision that gave us our Moon (and thereby stabilized the rotation axis of our planet, which was another great good)?

http://www.ingentaconnect.com/content/bell/igr/2002/00000044/00000002/art00003
http://www.episodes.org/backissues/242/93-101%20Allen.pdf
http://arxiv.org/ftp/arxiv/papers/0709/0709.1303.pdf
http://www.aepect.org/astenosfera/astenosfera/documentos/DOC_8.htm

Why is there water?

...And God said, Let there be a firmament in the midst of the waters, and let it divide the waters from the waters. And God made the firmament, and divided the waters which were under the firmament from the waters which were above the firmament: and it was so. Gen. 1:6-7

As Terrans, we have little appreciation of the rarety of liquids in the Universe, because we see liquid water all around us. However, ask yourself: what other liquids do you commonly see in large volume? Perhaps petrol, perhaps alcohol - and that's about it. This lack is not accidental. Fewer than 400 out of the four millions of known chemicals form liquids, and most of these are gooey oils formed by oligomerization of organics. This is chemical perspective. Astrochemical perspective is no better. If you discount magnetized plasma, liquids are almost unheard of in our Galaxy. On this planet, the prevalent liquid is not water but molten rock and iron. In the solar system as a whole, there is actually more liquid petrol than liquid water: inside the giant planets, methane is morphed into compressed, liquid hydrocarbons; there are three earth masses of gasoline inside Jupiter alone. Most of the water in our system is in the form of "dirty" amorphous ice in the comets and asteroids, where this ice only occasionally melts, e.g. during certain collisions. In the outer space, the water is either "dirty" ice or vapor; other liquids fare no better. There will be plenty of liquid water in the solar system one day, when our Sun will expand and become a nova, as the Oort cloud of comets will melt and evaporate
http://www.astrobio.net/news/modules.php?op=modload&name=News&file=article&sid=164&mode=thread&order=0&thold=0
That's a nice way of producing a lot of liquid water, but it is not a sustainable way. If you want to have a lot of liquid water for a decent time, say 2-3 Gyr, you better make yourself a rocky planet. Ditto for other liquids; the list of suitable liquids is short. Chemical synthesis of a large body of hydrocarbons requires either extreme conditions or low temperature, and the same goes for many other liquids composed of small molecules (methane, H2S, N2). One can have the ocean of liquid methane or nitrogen, but the temperature will be prohibitively low for most chemical reactions to occur, and such liquids poorly dissolve chemicals and ions in the first place. Water, H2S, supercritical CO2, ammonia, and a few lower hydrocarbons are probably the few choices one can ever have, and water is by far the most abundant and practical choice.

Is it difficult to put a hydrosphere on the planet, to part the waters? Not really. Look at our own solar system. Earth has it, Jovian moon Europa has it, both Mars and Venus had it in the distant past. Water (ice) is introduced during the accretion of rocky planets, gets trapped inside the interior and then outgassed into the atmosphere. Once the latter cools down below the critical point of water, you have your liquid water cycling between the atmosphere and the surface. Another mechanism for the delivery of water is cometary bombardment; perhaps as much as 10% of our water came this way. The formation of the hydrosphere happened in our system several times, and we presently know that it happened in other planetary systems too,
http://www.astrobio.net/news/modules.php?op=modload&name=News&file=article&sid=2394&mode=thread&order=0&thold=0
http://www.astrobio.net/news/modules.php?op=modload&name=News&file=article&sid=2311&mode=thread&order=0&thold=0

...On Earth, much of the water could be derived from Mercury-sized planetary embryos that formed in the asteroid belt beyond 2.5 AU.The higher D/H and impact modeling (significantly different than for Earth due to Mars's smaller mass) favor a model where Mars accreted a total of 6% to 27% the mass of the current Earth hydrosphere. The corresponding WEG would be 0.6 - 2.7 km, consistent with a 50% outgassing efficiency to yield ~500 m of surface water. An alternative to the cometary and asteroidal delivery of H2O would be the accretion via physisorption during the formation of the terrestrial planets in the solar nebula. This would be consistent with the thermodynamic estimate of ~2 earth masses of water vapor within 3 AU of the solar accretionary disk, which would exceed by a factor of 40 the mass of water needed to accrete the equivalent of 50 Earth hydrospheres per terrestrial planet. Even though much of the nebular water may be lost due to the high temperature environment of the accretionary disk, it is possible for physisorption of H2O on accreting grains to retain nearly 3 Earth hydrospheres of H2O at 500 K. (Wiki)

...On Earth, the primordial atmosphere was carried away by the solar wind that at the time of the formation of the Earth was much stronger than today, and so escaped the Earth until it had about 40% its current radius (and gravity could retain the atmosphere). Later through volcanism came the creation of a newer atmosphere, which may also have contained water-vapor released from the earth’s interior. With the development of a solid earth’s crust and further cooling down, the water vapour condensed and hence formed the first oceans. The large amount of water that is present on the Earth in comparison to other earth-like bodies cannot be alone explained by that released from the earth’s interior. The planetesimals formed in a period of the early Solar system, when there was relatively little water around. The closer to the sun one was, the higher the temperature and the less water present. However, outside the solar ‘snow line’, which lay roughly where the Asteroid belt is today, water could be found in considerable abundance. Carbonaceous chondrites, which it is generally agreed formed in the outer reaches of the asteroid belt, indicate a water content of sometimes > 10% of their weight, whereas common chondrites or enstatite chondrites from the nearer regions of the asteroid belt comprise less than 0.1% of their weight in water. It can be supposed that during the accretion of the planetesimals into planets and the loss of the primitive atmosphere would result in the larger proportion of the originally present water being lost. Hence it is assumed that the majority of the water present on the Earth today came from the outer regions of the Solar System. That the Earth’s water originated purely from comets is implausible, as a result of measurements of the H/D isotope ratios for comets. The largest part of today’s water comes from protoplanets formed in the outer Asteroid belt that plunged toward the Earth, as indicated by the D/H proportions in carbon-rich chondrites. The water in carbon-rich chondrites point to a similar D/H ratio as oceanic water.
http://astrobiology.arc.nasa.gov/workshops/1996/astrobiology/speakers/pace/pace_abstract.html

So, parting of the waters is not that hard. The tricky bit is retaining this water in the liquid state for eons by building the appropriate "firmament." Nature, as I pointed above, dislikes liquids in general and liquid water in particular, and it will do everything possible to vaporize this liquid water off the surface or freeze it into ice. Retaining liquid hydrosphere for billions of years is a fit that requires much more than sheer luck. It requires a place where the impossible is possible, and the improbable is probable - our Earth.

Water is a problematic molecule for making durable hydrosphere, because its vapor is very photoactive in the UV. On other planets, such as Venus, gaseous water in the atmosphere is rapidly dissociated by solar radiation, and the released hydrogen is ionized and blown away by the solar wind. This effect is slow, but inexorable. Unless water is mostly frozen, so the partial vapor pressure is low (as on Europa), all of the surface water will be gone in 1-2 Gya. There can be some replenishment of liquid water by continuing outgassing and cometary delivery, but these sources cannot beat photolysis in the long run. On Mars, small size and thin atmosphere resulted in the nearly total loss of surface water. Perhaps it could've been slower if Mars had global magnetic field shielding its atmosphere from the solar wind, but its dynamo shut down very early in its history, as its core cooled down. Venus had been dealt even worse card. Its initial store of water was larger than ours, but the planet was too hot and having too thick atmosphere. Its dynamo also shut down as the planet's rotation was slowed down to naught by the tidal forces of its own thick atmosphere. Too thick is bad and too thin is bad. So, how did we manage to retain our hydrosphere for 4 Gyr?

The answer to this question is unknown, but part of the answer is the proverbial "firmament:" our atmosphere. It has never been too thin to allow a lot of water vapor to be photolyzed in the upper atmosphere. It has never been too thick to despin our planet completely (which is a difficult task anyway thanks to our Moon). Our geomagnetic dynamo never shut down, and our magnetic field still protects us from the solar wind. And this dynamo never shut down largely because at the right moment our planet found a unique way of cooling itself by plate tectonics - which was facilitated by the subduction of liquid water into the mantle. We have another heavenly layer of protection - the ozone layer that screens water molecules in the stratosphere from the UV photolysis. Such a layer can only be acquired and sustained through photosynthetic production of oxygen by splitting of liquid water. That, of course, requires Life. The ocean of liquid water sustains Life, but Life is sustaining the long term stability of the ocean by actively changing the composition of the atmosphere. It removes the excess of CO2 that may result in runaway hothouse of Venusian proportions. Through denitrification, it keeps inert N2 in the atmosphere -- in order to have the right pressure without the greenhouse effect. It adds O2 that keeps water vapor from being blasted apart. And it does all of that since exactly the time when the last body of liquid water has been lost on Mars and Venus. That we got our stock of liquid water might have been accidental, but it is no accident that we still have our oceans. Having oceans of liquid water for a short while is easy. Keeping them on is a lot of hard work.

Of course we were lucky, I would not argue with that. We are at the right distance from the sun to get the heat budget which makes keeping the ocean possible. That necessary condition, however, is very far from being the sufficient one, and the habitable zone is actually pretty large, so one of the terrestrial planets was bound to be there. Just being in this zone works for a while, but then one's luck runs out forever. It was not given that Earth will be a pale blue dot 4.5 Gy after its creation. There were several snowball episodes 500-700 Mya when we faced the real prospect of becoming a frozen planet. The position in the solar nebula was not enough, the chemical composition was not enough, the size was not enough. Everything: geochemistry, geophysics, geology, atmospheric and ocean chemistry - all of these had to combine in just the right way to make long-term habitability of the planet possible. And still that is not enough. There should be Life on the planet.

Why do we have our water?

Interlude 1: the missing day of creation?

At the end of 1:6-7 essay, I observed that in order to create a habitable world complete with land and water, this world has to be seeded with Life at the very first opportunity. There is no time for "billions of years of prebiotic evolution," contrary to what you may have heard. The window of opportunity is very short. Any delay will seriously impact the habitability of the world 1-2 Gyr down the line. If the photosynthesis, denitrification, and sulfur recycling are delayed, the composition of the atmosphere will not be adjusted at the right time, and most of the liquid water will be gone. Without the continuous presence of the oceans, plate tectonics will not start, and the planet will begin to cool through volcanism. Then, not only the oceans and the land would be lost, everything will be lost. Life has to be present from the very onset; it is part of the "firmanent" that makes the planet habitable. Here by "Life" I mean a very specific form of life: the prokaryotic life, the Bacteria and the Archaea. It is their activity which makes this planet habitable.

There are two schools of thought about the Prokaryote kingdom. One is to bundle it with the eukaryotes (that descended from the prokaryote symbionts about 1.6 Gya) into one all-embracing "Life." This view ignores the fundamental difference between these two kingdoms. This is understandable because we do share common ancestry. Furthermore, the eukaryotes and the prokaryotes do look similar: for both, the basic unit of living matter is a cell. For this reason, the procaryotes are often mistaken for individual organisms. Such a view comes naturally to us, as we are individuals. However, the prokaryotes do not have "selves." There is no limit on the exchange of genetic information between them. There are physical barriers (e.g., different metabolic organisation) but these are breachable. Bacterial plasmids can be swapped via conjugation, without the direct contact, or through triparental mating (via another bacterium). Because cloning takes precedent over everything else and it costs energy, duplication of superfluous genes is prohibitive, and these are either lost or returned to the common pool - that is, to the prokaryotes that may need these genes for survival. Bacterial genomes form one continous gene repository; the sum total of all procaryotes is a single species. The "bacterial species" one hears about are ecotypes and genuses. This viewpoint was late on arrival, because the initial focus of microbiologists was on pathogenic bacteria that parasitize on specific eukaryotes, e.g. humans. Such bacteria very narrowly specialize so they do "speciate" in a restricted sense, although this only means that gene transfer is frustrated. This speciation is secondary development to the origin of Eukarya and it is not important in the grand scheme of things. Prokaryotes and Eukaryotes are not parts of a single Life, as these are two entirely different concepts of life. At this conceptual level (as opposed to their biochemistry and shared ancestry), these two kingdoms have nothing in common. One of these concepts (eukaryotic life) is domestic in origin. Another concept (prokaryotic life) is very ancient, and it may or may not be of terrestrial origin.

There is another, perhaps even more important difference. Prokaryotic life is the crucial part of planetary chemistry, providing the driving force for homeostasis on this planet. These two are so intricately meshed together that considering them apart can not be done even in principle, especially when you look into the distant past. The idea of indivisibility of procaryotic life and Earth's geochemistry is called Gaia hypothesis. Its central tenet is that the biota manipulates the environment for the purpose of the stabilization of this environment for its own benefit. One cannot deny that there is abundant evidence for this sort of manipulation on Earth. In strong Gaia hypothesis, the prokaryotes and the Earth form the single entity - Gaia - and only this composite entity can be rightfully called Life. From this standpoint, Eukarya are the separate Life that is parasitic on Gaia. Admittedly, this is a radical idea that requires redefining and rethinking what we call life. So be it. In the following, this idea will be accepted as the premise:

There are two Lives on this planet that coexist side by side: one is Gaia, another is Eukarya. The latter separated itself from Gaia by the invention of the self.

There is little doubt that Eukarya has the terrestrial origin and as such is unique in the Universe. How about Gaia? My belief is that procaryotic life is exogenic; as such, it is not unique. I do not know where and how this particular form of life have began and how it got onto Earth (not that the ways of the delivery are completely unknown). For all I know this form of life might be very common or exceedingly rare in our Galaxy, but in either case it is not of our world. It got full advantage of our home planet and locked onto it by transforming it into Gaia, all the way adaptating to its new home, as befits Life. I do not want to go into the arguments in favor of Panspermia, because at the present time it is just an opinion. The strongest argument is that the interval of time between the first cyanobacterial mats (stromatolites) occurred in the geological record and the time the planet cooled down to sustain liquid water was very short, and this period of time seems to get shorter with every new measurement. One has to believe that fully formed cyanobacteria have appeared from scratch in just 200-300 Mya. It is easier for me to believe that the world is flat and rests upon a turtle. As pointed above, a habitable world has to be seeded at the very first opportunity, and that is what happened on this planet. You can make whatever you want of this fact.

This series is not about the creation of the Universe or life as a cosmic phenomenon. My scope, like the scope of the book of Genesis, is the creation of OUR world. Blending of the exogenic, prokaryotic life with our planet into Gaia is part of OUR story, but the origin of the prokaryotic way of life per se is not, for reasons I stipulated, and so it is omitted from the narrative. One may consider "the origin of life" on this planet as part of the "firmament" building. In the Gaian view, creating a habitable planet and seeding it with life is one and the same act. And it has to be this way provided that the world is intended for long-term habitability.

I needed this lengthy interlude to explain why "the origin of life" has been excluded both from the book of Genesis and this narrative. The only Life that originated on this planet is the Eukarya.

Why is there light?

...And God said, Let there be light and there was light. And God saw the light, that it was good: and God divided the light from the darkness. And God called the light Day, and the darkness He called Night. Gen. 1:3-5

This verse is especially loved by astrophysicists and cosmologists. Decoupling of the radiation from matter, reionization of the Universe, lighting the first generation of stars, and the formation of proto-galaxies can all be interpreted as "let it be light." Once the solar system had been made, the rest was mere technicality: there is a (nearly) everlasting source of radiative energy and Life takes advantage of this source. Alas, this is not true. The Earth and Venus started from nearly the same atmospheric composition. On our planet, there is plenty of sunlight at the sea level. On Venus, the sunlight is nearly completely blocked by sulfuric acid clouds and haze: the perpetual source of energy created the perpetual Hades. On chilly Titan, methane/N2 atmosphere produced thick haze enveloping the planet resulting in anti-greenhouse effect further freezing it. The haze is also present in the atmospheres of Jupiter and Saturn. It is hard to have the organics, such as methane, AND reducive atmosphere and avoid the formation of haze that blocks sunlight.
http://geology.geoscienceworld.org/cgi/content/abstract/29/11/1003

The flux of energy is nice, but the energy per se does not matter; what is required for Life are gradients of energy and entropy. What makes Sun the suitable source of energy is the low entropy of its radiation, which in itself is the consequence of gravitational accretion. The radiation has to be absorbed during the day and re-emitted into space at the shorter wavelength during the night. Without the planetary rotation one gets a bathhouse world that is prohibitively close to thermal equilibrium. The fast rotation of the giant planets also tends to minimize the gradients. The rotation axis should point in the right direction: the obliquity should be small, otherwise there is thermal imbalance between the lit and unlit halves of the planet. Before the collision that gave us the Moon, the Earth had the day of 3-4 hrs and chaotic obliquity, like Mars. What lengthened our day and stabilized the obliquity was the very collision that gave us the Moon and our land.

Today, ca 25% of solar radiation is reflected and scattered back before it reaches the ground, and 20% is absorbed; 60% reaches the ground. On Venus, the haze, clouds, and junk in the atmosphere (SO2, H2S, HCl, HF) absorb most of the incoming light. The haze and clouds rise as high as 50-80 km above the ground and blanket it completely. All of the light shorter than 350 nm is absorbed, and only 14% reaches the ground. The sulfuric acid is formed when O generated by photodissociation of CO2 reacts with SO2 and water vapor in the atmosphere. If there is no circulation of liquid water through the atmosphere, the SO2 and CO2 are not removed, aerosols form, and the insolation goes down. Venus gets twice the radiation flux of the Earth, but there is < 1/2 of the light at the ground level. Observe that Venus is not Earth. On Venus, one does not have to worry that the planet will freeze over, no matter what is the atmospheric composition. On the early Earth, this was a concern: without the greenhouse gases, the temperature would plummet to -40 C, and the oceans will be covered by 300-1000 m of ice. This does not exclude lithotrophic Life, but completely excludes phototrophic activity. To have liquid water world rather than sub-ice world, the transformation of the atmosphere has to proceed in a very precise way.

In order to have vigorous photosynthesis (required for retaining the oceans) the light has to reach its destination: the sea level. The solar radiation should be reasonably filtered to remove the harshest UV light, otherwise the radiation will sterilize the planet. Presently (for the last 1.8 Gys), the protection of water vapor from photodissociation and the rise of temperature in the stratosphere that puts the lid on vapor transfer to the upper atmosphere are due to the absorption of the UV light by ozone. This ozone layer had to be built, but it cannot be built rigth away, as the atmosphere has to become oxic first. The oxidation of the atmosphere has to proceed in such a way that there is sufficient level of greenhouse gases to prevent freezing of the planet.

The problem is that the condition of the early terrestrial atmosphere was quite similar to that of Venus (minus heat): the atmosphere was reducive, contained lots of CO2, methane, NH3, SO2, etc. The Sun was fainter through the Archean, and having these gases was very important for retaining liquid water. However, such gases make haze when cooked by the Sun. Without the oxygen to oxidize the gunk, the haze begins to absorb polymers made by the photolysis of CH4 (tholins). Water scrubs CO2 and SO2 out of the atmosphere, removing the haze, but this takes time, so hazy conditions prevail for a long time. The transparency of the anoxic Archean atmosphere was probably rather poor. Quite possibly, it has to be this way: the tholine haze worked as a sunscreen protecting CH4 and NH3 below the haze level from the UV light. The haze was required to keep the early planet from freezing, but it blocked the sunlight interfering with photosynthesis in the oceans and slowing down the oxygenation required for long-term stability.

There is little understanding of the properties of the early atmosphere and what had changed during the Great Oxidation Event, as it is called. The dogma is that it was photosynthesis itself that changed the condition, in one or more steps, but the transition in the mantle oxidation states and the escape of H via photolysis of water and methane might have been involved too. A few reviews can be found here
http://www.jstage.jst.go.jp/article/jmps/100/5/184/_pdf
http://www.amazon.com/Proterozoic-Biosphere-Multidisciplinary-Study/dp/0521366151
There are a few ideas as to what might have happened. One is that the oxygenation happened in two distinctive bursts. In the first one, that occurred extremely early in Earth's history, the level of photosynthetic oxygen rapidly rose to a small fraction of its present level (about 1e-5) and stabilized there for a long time. This was sufficient to clear the skies for sustainable, if inefficient, photosynthesis. This oxygen slowly oxidized what was there to reduce, and as soon as that happened, there began runaway oxygenation that was followed by stabilization of O2 at a much higher level. Other ideas involve the reduction of volcanic flux of CO2 as the planet cooled down and the gradual loss of H to space. Yet another theory focuses of the main sink for O2: the organic carbon. The theory suggests that it was sinking through methanogenesis: the carbon was converetd to CH4 by the Archae, the latter was photolyzed, and the released H was lost to space, causing the net increase in O2. Ironically, it might be the activity of methanogenic procaryotes that aided the oxygenation and prepared their demise. Once the photosynthetic and abiogenic production of O2 exceeded the input of reducing gases, the skies cleared and the runaway photosynthesis began.

These theories have interesting implications for habitability. First, it appears that the methanogens were NEEDED for the subsequent oxygenation of the atmosphere. Second, the choice of the main photosynthetic pigment, chlorophyll, which looks idiotic from the standpoint of the present (most of the sunlight penetrating the atmosphere is not absorbed by the chlorophylls) makes perfect sense. Due to the strong filtration of the sunlight by the haze, the pigments should absorb mainly in the red (the chlorophylls absorb in the 620-680 nm region). The chlorophyll and carotenoid co-pigments have the onset absorbances at 350-400 nm, which is close to the spectral cutoff of the sunlight that penetrates Venus' clouds. The action spectrum of bacterial reaction centers has a dip at 550 nm, where the solar radiation at the sea level peaks. That's now. Back then it was further down the red.

The reconstitution of the atmosphere was a perilous ordeal. As CO2 levels dropped, the haze thickened and greenhouse effect subsided, causing disruptive glaciations.

...As CO2 levels fell due to weathering, levels of CO2 and CH4 became about equal. This caused the methane to aerosolize into fine particles 2.7 Gya. It further removed methane from the atmosphere and the haze filtered out light (anti-greenhouse cooling); both caused further cooling, perhaps a temperature drop of 40 to 50 C. Eventually, about 2.9 Gya, the greenhouse collapsed, and the Earth's first glaciation occurred. The weathering slowed down -- there was less carbonic acid to erode the rocks, but volcanoes were still spewing into the atmosphere large amounts of carbon from recycled oceanic crust. Eventually the CO2 level climbed again. By 2.5 Gya, an enormous amount of new continental crust had formed -- about 50% of the present area of continental crust. During this second cycle, weathering of the larger amount of rock caused even greater atmospheric cooling, spurring a profound glaciation about 2.3 Gya. http://news-service.stanford.edu/news/2004/june2/lowegeo-62.html

To conclude, "Let there be day and night" was a program that stretched over 2-3 billion years and required meticulous planning. Part of it was a one-day job of giving the Earth the right amount of angular momentum and stabilizing its rotation through the formation of the Moon. Other parts of the program took longer. For efficient photosynthesis and retaining of liquid water, one needs total reconstitution of the atmosphere and removal of light-absorbing haze -- without the loss of the greenhouse. There has to be small level of oxygen present right away, in order to avoid blocking of the sunlight. That is yet another rationale to introducing photosynthetic Life as soon as possible. Not only the phototrophs, but also the methanogens have to be present from the onset to make the transition from anoxic to oxic atmosphere smooth and provide the sink for carbon. In fact, the whole team shall be present to take care of the C, N, S, and O cycles. Still, one has to be prepared for an occasional setback, so Gaia has to have a lot of resilience. Creating habitable worlds is not easy, and there is no room left for accident.

Why is there light?

The face of the waters

...And the earth was without form, and void; and darkness was upon the face of the deep. And the Spirit of God moved upon the face of the waters. Gen 1:2

We have seen in the previous installments how difficult it is to make a rocky planet habitable over a long duration of time. Is there a "natural" solution to habitability, a solution that does not require such great effort? There could be such a solution, and it has been found very recently, in 2003. It remains largely unknown to people other than planetologists. It is called the "ocean-planet." I believe that this type of a planet is where prokaryotic Life is from.

The problem with the telluric planets in the solar system is their small size, which is the cause of all trouble. What would happen if the planets were larger? If the planet is greater than 10 earth masses, it accumulates and retains hydrogen and helium, so that is another dead end, literally. If the mass is 2-8 earth masses (such planets are called super-earths), there are two solutions: one is a rocky planet, like Earth, Mars, and Venus; such a planet may or may not retain a thin hydrosphere. Short of a miracle, this hydrosphere will be lost in 1-2 Gyr. However, if a large protoplanet is formed far from its sun, its composition will be about 50-50 rock and ice, like that of the comets. In our system, all the moons of the giant planets except Io are of this type, but these are too small to become ocean-planets. If a large icy planet subsequently migrates towards its sun, then the ocean-planet is formed. Such migrations are common and occurred in our own system: the planets move invards or outwards as they interact with the turbulent gas of the disk. In the solar system, the icy planetoids at the outskirts of the disk were captured by the giant planets, becoming their satellites or plunging into them. However, large icy planets might be more common in other systems and these planets stand a good chance of moving closer to their suns and melting there.

On such "hot" ocean-planet planet, the ocean is not skin-deep, as on Earth; the depth of the superocean is tens or even hundreds of kilometers, it is all water. A planet of 2 earth masses with the surface temperature of 30 C will have the ocean that is 130 km deep. The bottom is not rock either; under high pressure, water is turned into ice; the rock-iron core is isolated from liquid water by hundreds of kilometers of ice. There is so much water on the ocean-planet, that it cannot be lost to space no matter what the planetary chemistry and atmospheric composition might be. The primordial atmosphere is not lost during the accretion, so its initial composition will be water vapor, CO2, and ammonia. The latter will be turned to nitrogen in just 2 Myr of UV photolisys (at 1 au from a G2V star). The atmosphere will be clear and rich in N2, just like ours. Water vapor will be photolyzed too, but there is so much of it that there is no danger of ever running out of it. The pressure of N2 may be very substantial early on, but it excess N2 is slowly dragged away by hydrogen flow into the outer space. An interesting feature of the ocean-planet is the possibility of massive abiotic oxygenation due to water photolysis. Unlike the rocky planets in our solar system, the ocean-planets do not have exposed rocks that need be oxidized before oxygen begins to accumulate in the atmosphere.

The exiting thing about super-earths is that the first of such planets has already been discovered in 2005 around dM4 (red dwarf) star GJ 876d, which also has two other (Jupiter-like) planets.
http://www.journals.uchicago.edu/doi/abs/10.1086/491669
Super-earths are not fantasy; GJ 826 is just 15.4 parsecs away - it is the closest multiple exoplanetary system to our Sun. Curiously, chlorophyll absorption spectrum closely matches the emission spectrum of red dwarf stars. Another interesting fact about the super-earths is that plate tectonics is inevitable on such planets:

...as planetary mass increases, the shear stress available to overcome resistance to plate motion increases while the plate thickness decreases, thereby enhancing plate weakness. These effects contribute favorably to the subduction of the lithosphere, an essential component of plate tectonics. Moreover, uncertainties in achieving plate tectonics in the 1 regime disappear as mass increases: super-Earths, even if dry, will exhibit plate tectonic behavior.
http://www.journals.uchicago.edu/doi/abs/10.1086/524012

We reach the following conclusion: the conditions that are so difficult to achieve and maintain on a small rocky planet (and are impossible to achieve there without active participation of prokaryotic biosphere) emerge very naturally, in a completely abiotic way on the massive ocean-panets. The atmosphere is clear, there is liquid water, there is CO2, N2 and O2, there is plate tectonics preventing massive volcanism, etc. The only thing that is missing is land, so that's our claim to originality. The ocean-planet is a type of world where billions of uniterrupted, unhurried years of pre-biotic evolution are possible. When Life would appear there, it will be adapted exactly to the conditions that occur, after so much strife, on Earth. "Terraformation" is a joke: what has been laboriously replicated are the conditions that naturally exist on super-earths; on earths, such conditions are totally unnatural. The story of habitable Earth began on a watery world that somehow - I do not know how - came into the contact with our planet and sealed its fate. The Earth was then without its present form, it was void, and darkness was upon the face of its deep. And then everything changed. The day on which this contact occured was the first day of our world, its true Beginning. Before that day, it was just astrophysics, not that it does not have its own store of surprises.

Now you know why the Spirit moved upon the face of the waters.

http://cips.berkeley.edu/events/seminars2005_2006/leger.pdf
http://www.physorg.com/news89627725.html
http://www.journals.uchicago.edu/doi/abs/10.1086/509800

Interlude 2: The Fall of Nature

Let us take the stock of the situation that existed before the emergence of the Eukarya. From 1.8 to 0.8 Gya, Earth was the Garden of Eden, the seat of prelapsarian Nature. Prokaryotic Life firmly entrenched itself in its new home and transformed it into Gaia. This form of life was both harmonious and complete. Far from being the "survival of the fittest" and endless, desperate adaptation to the ever changing environment, it modified and controlled the environment to fit its own needs. No further change was needed and there was indeed little change. As far as the Earth was concerned, Gaia was nearly omnipotent and it still is. Death and suffering were literally unknown to this single inhabitant of the planet. The loss of a bacterial cell to Gaia is what a loss of a single cell of our body is to us; the event of complete unimportance. The bacterial cell is primitive by the standards of eukaryotic organisms, but the gross total of the Prokarya and its terraforming operation was nothing but unimaginably complex. I often hear claims to the effect that “human brain is the most complex object in the Universe.” This is flattering, but I am skeptical that it is true even in our world. One can argue that the brain houses intelligence and Gaia does not. I am not sure of that either. It does not have our kind of intelligence. However, our intelligence is not brain; it is what happens in the brain. To an onlooker, the brain is a “piece of meat” that has no purpose and no spark. Similarly, Gaia looks to us like so much slime distributed over the planet. That does not exclude that it has intelligence; certainly it has the complexity that would make intelligence possible. The irony is that our earning to find alien “brothers in intelligence” may be not only misplaced (we are the only ones who have ours – human – type of intelligence), but has been long fulfilled: the alien intelligence has been around from the beginning of our world. It only characterizes our own intelligence that we live in the middle of it and chose to ignore it. All I can say is that the search for “extraterrestrial intelligence” as it is presently conceived is likely to be a failure, not for the lack of the intelligence, but for our inability to recognize it. That being said, the question of the nature of Gaia is not part of this story, because this story happens to be ours. Let's move on.

Nobody knows how the Eurkarya originated; there are only speculations. I have written about some of these theories here http://shkrobius.livejournal.com/84165.html and here
http://shkrobius.livejournal.com/67551.html and there is little point in revisiting the subject, because these are wild guesses. The important thing is that the eukaryon was the fruit of uneasy merger between two main forms of prokaryotic Life: Bacteria (that gave the Eukarya mitochondria and plastids) and Archaea (that gave us its genetic machinery). This merger was a miracle, if by a miracle we understand the highly unlikely, possibly unique event. The bacterial contribution solved the energetics problem of developing and maintaining complex genomes in an individual cell. The protoeukaryon chimera no longer needed to borrow from and contribute to the common gene pool. For the first time, wholly individual existence became possibility. This possibility has been realized, and new form of Life came into existence. Nature has fallen.

The new terrestrial Life was full of strife. Death has arrived immediately and in staggering variety. Whereas Gaia is infinitely pliable and coordinated, the individual has to adapt to its environment, and this adaptation can not be permanent. Not only the individual cannot last, even the entire line of this individual’s descendants (a species) cannot last forever as the environment changes: the average longevity of a species is less than 4 Mys. Individual adaptability has its limits and those are readily reached. The more complex is the individual, the shorter is this span, which is almost imperceptible on the time scale of Gaia’s existence. Furthermore, it soon became apparent that one individual can predate and parasitize on another, even of its own kind. For example, one can murder one’s sex partner after mating, and why not? Another individual of the same species is useful for sex, but has limited uses in other ways, if we discount communal projects. Worse, the individual became fair play to Gaia from which it separated. Again, why not? The individual’s interaction with Gaia has been one sided from the onset. It uses the genetic richness of Gaia as the source of its own genes and parasitizes on Gaia's body, making no reciprocating contribution. There is no advantage to Gaia to spare it. The Eukarya are the rich source of nutrients and nice walking machines for proliferation. A new habitat has been added, and it was immediately occupied. The triumph of death, murder, pain, and suffering was instant and complete. Such became the character of terrestrial Life.

Could it be different? I do not think so. The strife is the logical consequence of having the self. Life without strife is possible and it is right before our eyes, for all to see. But such Life is not based on the concept of the self. The Life that is based on this concept is the survival of the fittest, the endless struggle to adapt and continue one’s line, which is full of misery and privation. Having it both ways is no more possible than having a square circle. The possibility for the self has always been present in Gaia; in this sense, it has been preordained. Perhaps it was only the question of time and chance, when and where it would be realized. By chance or design, it occurred on Earth. One form of Life has eaten the forbidden fruit of individuality and banned itself from the Garden of Eden.

Was there a tempter – an otherworldly being who already had the self and bestowed it upon us? This is the question that each of us has to decide for oneself. What form of Life would YOU like to spread beyond this planet? One day, this choice might be ours.

In the beginning God created the heaven and the earth. Gen 1:1

Before contemplating the creation of a habitable world, some ground work has to be laid. At the very minimum one has to find a light planet in a planetary system of remarkable stability. Two scenarios have to be avoided: one is the migration of this planet out of the habitable zone or its collision with another planet. The second scenario which has to be avoided is constant heavy bombardment of the chosen planet by asteroids and comets. Such bombardment has its uses for the delivery of material at the Hadean stage, but it can be deadly at a later stage, though an occasional collision can do wonders for evolution. The showers and the migrations are closely connected. The peak of the bombardment of the Earth and the Moon has been around 4.5 Gya when the Moon had formed. One such impact might be beneficial, but continuous bombardment of this kind is detrimental. A planet that is bombarded on every day of the week is not suitable for seeding Life on it. The bombardment of the Moon and Mars (and, most likely, the Earth) continued long after their accretion, well into Nectarian period, with a peak at around 3.9 Gya (the so-called late heavy bombardment). The early bombardment was by impactors in the asteroid belt that was achieving resonance stabilization with Jupiter. The late bombardment was quite different. The peak was very sharp (20-30 Myr) and the timing was not accidental: the most likely cause is the migration of outer gas giants towards the Kuiper belt. The current thinking is that Uranus and Neptune formed much later than Jupiter and Saturn (just around 3.9 Gya) and accreted very rapidly, in just 10-20 Mys. These planets should have formed closer to the Sun than their current orbits. The idea is that shortly after the formation, Neptune migrated outwards in the planetesimal-rich zone, rapidly grew in size and started to scatter the debris from this zone.
http://www.roe.ac.uk/~jkd/kbo_proc/koeberl.pdf

Again, one such bombardment episode might not be a big deal, but it is important that the migrations of planets stop early in the history of the system; otherwise the habitability may not be sustainable. The first evidence for photosynthetic Life comes right at the toes of the late heavy bombardment episode, which was perfect timing. By the way, it cannot be excluded that we should thank this bombardment for the delivery of prokaryotic Life from an ejecta captured from another planet.

The question is: how to achieve these two goals? Planetary systems are inherently prone to chaotic behavior, and there is ample evidence for such behavior for small objects in our system, including the demoted planet Pluto. Furthermore, both large and small exoplanets around other stars have been preselected (due to observational constraints) to include those that migrated close to their suns. The planetary migration is going on big way elsewhere, and the result are dying worlds. The consequences of planetary migration can be especially dire for light planets, like ours, that can be easily pushed inwards and outwards and even completely rejected. How stable is the current arrangement?

Earth’s orbit is, in fact, chaotic: an error of 150 m (which is 1e-9 in eccentricity) in the current position results in unpredictable orbit in just 100 Mys. Lapunov time of the entire solar system has been estimated between 5 and 10 Mys, meaning that the uncertainty of 1 km translates into the uncertainty of 1 AU in 100 Myr. These are crude calculations involving the planets only. When one factors in countless small bodies, it becomes apparent that no long-term forecast can be obtained by number crunching. The solar system may be unstable orbitally, but at least it is stable structurally: the orbits change but the planets remain near their present orbits over the lifetime of the Sun. There is an important caveat, though: the orbits of the giant planets are essentially regular, whereas the orbits of the terrestrial planets are largely chaotic. The relative stability of the giant planets has been maintained from the time the gas and extra planetesimals in the disk have been removed; but the inner planets are always in danger. The greatest chaos is for Mercury, it is less chaotic for Mars, and it is mildly chaotic for Earth and Venus. Once Earth is removed, the inner system becomes acutely chaotic. Amazingly, it is our Earth that stabilizes the orbits of inner planets. Luckily, the instability of Mercury’s orbit is largely inconsequential because of its small mass; would it be larger, the inner planets orbits would become chaotic. Still, there is a small chance that Mercury will collide with Venus in 1-3 Gyr
http://chaos.if.uj.edu.pl/~karol/pdf/solar.pdf, http://www.pnas.org/cgi/reprint/98/22/12342

…the Earth-Moon system (EM) plays an important dynamical role in the inner solar system, stabilizing the orbits of Venus and Mercury by suppressing a strong secular resonance of period 8.1 Myr near Venus's heliocentric distance. The EM thus appears to play a kind of “gravitational keystone'' role in the terrestrial precinct, for without it, the orbits of Venus and Mercury become immediately destabilized… Our basic finding is an indication of the need for some sort of rudimentary "design" in the solar system to ensure long-term stability. One possible aspect of such "design" is that long-term stability may require that terrestrial orbits require a degree of irregularity to "stir" certain resonances enough so that such resonances cannot persist.
http://www.iop.org/EJ/article/1538-3881/116/4/2055/980146.web.pdf?request-id=nlkdLibC3BGfS0MN3Ai7Kg

The main source of stability of the entire system is the heaviest of the giant planets, Jupiter. Not only it deflects most of the debri that migrates towards the sun, even small variation of parameters of its orbit will induce chaos in the orbits of the giant planets, with dire consequences. It is doubtful that any Life on Earth would be possible without Jupiter. But it is not just Jupiter; it is the entire organization of the solar system: there is dynamical separation between the terrestrial and Jovian planets:

...The difference in dynamical separation between terrestrial and Jovian planetary subsystems seems to be important. The terrestrial planets have smaller masses, shorter orbital periods, and wider dynamical separation. They are strongly perturbed by the Jovian planets, which have larger masses, longer orbital periods, and narrower dynamical separation. As a subsystem, the Jovian planets are not perturbed by any other massive bodies. Ito and Tanikawa have performed a set of numerical experiments to understand how these differences between terrestrial and Jovian planets affect their long term stability. They have considered various kinds of terrestrial planetary subsystems with equal dynamical separations and determined their typical instability time scales under the disturbance from the massive Jovian planets. They find that the terrestrial planetary subsystems with smaller dynamical distances are likely to become unstable in a short time scale (<10 Myr). This rapid instability is caused by the strong gravitational perturbation from massive Jovian planets. Thus it seems that the present wide dynamical separation among terrestrial planets is possibly one of the significant conditions to maintain the stability of the planetary orbits in Gyr spans. http://www.pnas.org/cgi/content/full/98/22/12342

Calculations suggest that the solar system is not only marginally stable, but it is also full: squeezing another planet will result in total chaos and rejection of planets. Quite possibly, there were more planets originally, but these planets have been lost – and their loss is what increased the distances between the remaining planets and made the relative stabilization of the remainder possible.

…the solar system, at each stage of its evolution, was always near the edge of instability. To maintain its marginal stability, the solar system has been eliminating objects on a timescale comparable with its age at every epoch. It follows that the solar system billions of years ago may have contained more planets that it does now. As the solar system matured, it managed to remain stable against the breakout of large-scale chaos by reducing the number of planets and increasing the spacing between them. The present number must be about as large (and their spacing about as small) as allowed by the system's long-term stability.

…Juric and Tremaine ran thousands of computer simulations to follow the dynamical evolution of 10 or more giant planets in a disk undergoing collisions, mergers and ejections. For simulations that begin with planets relatively close together, the ones that survive to the end have a distribution of orbital eccentricities that matches the data for the observed extrasolar planets. For simulations that begin with the planets farther apart, leading to fewer interactions, the surviving giant planets have lower orbital eccentricities, more like our own solar system. Most of the simulations end up with two or three giant planets, after the ejection of at least half of the initial population. The largest worlds left behind continue to grow by sweeping up smaller objects that remain bound to the central star. Making planets thus seems to be an extremely messy business.

… Barnes used computer simulations to examine the stability of extra¬solar systems having two or more planets. They found that almost all systems with planets that are close enough to affect one another gravitationally lie near the edge of instability. The simulations showed that small alterations in the orbits of the planets in those systems would lead to catastrophic disruptions. The prevalence of such marginally stable systems makes sense, if planets form within unstable systems that become more stable by ejecting massive bodies. The investigators remarked, "As unsettling as it may be, it seems that a large fraction of planetary systems, including our own, lie dangerously close to instability." Barnes went on to hypothesize that all planetary systems are packed as tightly as possible, as Laskar had suggested earlier. We have here a fascinating new hypothesis, which posits that our solar system and other mature planetary systems are filled nearly to capacity. The present configurations of such systems contain about as many planets as they can hold, spaced about as closely together as stability allows. Such is the expected outcome of the chaotic process that makes planets. A family of planetary embryos grows by feeding on a vast swarm of smaller objects in a debris disk until the system loses its brakes. Global instability then erupts, and the larger worlds consume or eject the more erratic ones until the system settles down into the mature state of marginal stability. http://www.spacedaily.com/reports/Are_Planetary_Systems_Filled_To_Capacity_999.html

...the asteroid belt certainly had much more material when the solar system was forming than it does today, and Jupiter was responsible for clearing most of that material out. As the solar system formed, Jupiter's powerful gravity perturbed asteroids to accrete into larger and larger objects - terrestrial "embyros" as big as Mars or bigger - then tossed them into very unstable elliptical orbits. Those that hit Earth when flung toward the inner solar system delivered the water that now fills Earth's oceans. That happened when Earth was about half its present size. A solar system with water-bearing asteroids but no giant planets might not evolve habitable worlds with oceans. http://www.spacedaily.com/news/life-01e.html

So, the order comes only after the period of great chaos, instability, and attrition resulting in the loss of half of the planets. The survivors are marginally stable, but there are no easy means to guess which planets will be the survivors and for how long. Note that Earth’s orbit is not only quite stable but also has very low eccentricity (0.03), which stabilizes the climate. That’s not normal: most calculations predict at least 10-20 times greater eccentricity than observed and all exoplanets exhibit this great eccentricity.
The orbital stability, of course, is only one requirement. The solar system itself should be stable in its orbit through the Galaxy. We have been lucky there, too, because the Sun lies within the galactic co-rotation radius: the orbital period of the sun equals the orbital period of the spiral arms, so we are permanently situated between two such arms. Would we be inside the spiral arm, we’ll see little of the night sky, as most of the starlight would be blocked by gas and dust (we’ll come to that later). Worse, the motion through the denser regions of the Galaxy can disrupt the Oort cloud showering us with comets. It is entirely possible that even minor perturbations of this kind, due to vertical oscillations of Sun’s orbit that change the cosmic ray flux, adversely affect Life on Earth. http://arxiv.org/abs/astro-ph/0602092v3

Given the number of things that have to go right over enormous spans of time and the near impossibility of predicting the chaotic dynamics, is it possible to choose a planet?

It seems to me that (i) any such attempt can be made only after most extra planets have been rejected and some degree of dynamical relaxation has been achieved, and (2) even then there is no guarantee that the planet will remain habitable in the long run. The best pick is a tellurian planet that contributes most to the overall stability of the system. In our system it is Earth. Another must is having giant planets that vacuum the system of debri and provide some measure of protection against bombardment by outer small objects and also provide regularity to the overall system. We have it too. The time and the place for biotic terraformation have been wisely chosen. Perhaps the best strategy is to “help” the system to assume stable configuration, by trial and error, e.g. by changing the orbit of one of the planets and waiting 10-20 Myr to observe the progress of dynamic relaxation. Of course, completely opposite approach is also possible: indiscriminate seeding all suitable planets with Life, throwing one’s hands up, and hoping for the best. That’s possible, but the attrition rate will be enormous. A prudent creator takes care of heaven and earth before embarking on a 4.5 Gyr long, high-stakes program.

Why is there Earth?

PS. See http://shkrobius.livejournal.com/103455.html?thread=338719#t338719 for pointers to recent reviews on chaos in solar system.

Why do we see stars?

...And God said, Let there be lights in the firmament of the heaven to divide the day from the night; and let them be for signs, and for seasons, and for days, and years: and let them be for lights in the firmament of the heaven to give light upon the earth: and it was so. Gen 1:14-15

This part of Genesis has been mocked frequently and mercilessly. The ignorant Hebrews which put this fairy tale together got it all wrong: the seasons, the Sun and the Moon, and - especially - the starlight in heaven - all of these fixtures have been around from the onset. Yet the tale claims that these came to pass only after the emergence of plants.

I do not share in the fun. There is a good reason why the seasons are mentioned only after plants in the book of Genesis. It refers to a particular event in Earth's history which we'll examine later. However, let us get the astrophysics right first. There were stars in the firmanent of the heaven long before the beginning. Were these stars seen from Earth during the night? As we discussed, the evolution of atmospheric transparency is unresolved issue; the skies have not been clear all of the time. However, there is more to it. We take it for granted that the region of space around the Sun has always been relatively clear, that the current situation when it is largely free of obscuring gas and dust has persisted over a long period of time. I do not see why is that self-obvious, and I do not know of any astrophysicist who ever made such a claim.

In the Beginning, that was certainly untrue because the solar system was born deep in a nebula where the concentration of gas and dust were very high. We know that because our sun is rich in "metals" (elements heavier than He), which is actually unusually high for the star of its class, age, and location in the galactic disk. The difficulty seeing through the dense clouds is the chief reason why so little was known about star formation before infrared astronomy matured. This nebula was reprocessed remains of the earlier generation of stars. The collapse has been preceded by a supernova explosion: the shock wave of this explosion densified the gas cloud and made the star formation possible. Alas, some other world paid the ultimate price for the formation of our own. Several young stars were formed as a result of this collapse; that is common scenario because the formation of a lonely star is statistically insignificant. The new stars of the main sequence are usually born as binaries or triple systems, with a smaller fraction of larger gravitationally coupled clusters. The binaries are stable, but larger clusters tend to lose their lighter components until only binaries remain; it is likely that our Sun's has been rejected from the swarm of its celestial sisters. All these events occurred when the Sun and its companions was still inside the dense cloud. As the light from bright young stars cleared the inner part of the cloud, these stars have been seen from the Sun, but little else was observable.

Why do we see many stars today? That is not too common, and the reason is the combination of several factors. First, the Sun is situated in the relatively empty space between two dense spiral arms of the Milky Way. Not only it sits there safely, it rotates in an uncommonly circular orbit around the galactic center with the same angular velocity the Galaxy itself rotates at the Sun's distance from the center, so the dense arms do not catch up with us, at least presently. If we were inside these spiral arms, we would see a few close stars, but most of the starlight would be obscured by clouds and dust. These arms are dangerous places, where gas is collected and new stars are being formed. The radiation of these stars and their frequent explosions are capable of destroying billions of years of diligent work. Second, the Sun sits near a cloud (Local Fluff) at the edge of a huge cavity called Local Bubble that was formed by an explosion of a supernova (Geminga), at 170 pc away from the Sun, possibly only 100 kya. The bright stars in our sky - Vega, Altair, Fomalhaut, Arcturus (Gould Belt OB stars) - also sit in the Local Fluff. The Hyades, Algol, and Aldebaran sit inside the bubble.

...the Local Fluff extends about 3.5 pc. The pattern of emission of stars in this region indicated a dense cloud located about 17-35 pc from the Sun towards the Galactic Center in Sagittarius. The Local Fluff is the low density, ionized outer layers of this cloud, and that the Sun has just recently entered the outer regions of this dense cloud. The solar system is, apparently, moving along a path that is certain to take us closer to the Sco-Cen expanding superbubble. The 'wall' between the Local Bubble and the Sco-Cen bubble now seems to consist of an increasing density of cloudlets of varying size and density. The Sun, after apparently spending many hundreds of millennia in quieter regions of the Local Bubble, is apparently now moving nearer one wall of this cavity towards us from the direction of Scorpio/Centaurus. Rather than a smooth wall of material, it consists of many individual pieces and cloudlets. When the solar system enters such a cloud, the first thing that will happen will be that the magnetic field of the Sun, which now extends perhaps 100 AU from the Sun and 2-3 times the orbit of Pluto, will be compressed back into the inner solar system depending on the density of the medium that the Sun encounters. When this happens, the Earth may be laid bare to an increased cosmic ray bombardment. http://www.astronomycafe.net/qadir/q1372.html

One portion of the Local Bubble's wall appears to have collided and merged with the shell of another enormous bubble of hot, ionized gas that's called (Radio) Loop I. Located far above the galactic plane, within 490 ly of the Local Bubble, Loop I's brightest feature is the North Polar Spur, which is thought to be created by supernovae and stellar winds from the 13 Myr old, Scorpius-Centaurus Association of young and massive, OB-type stars. In addition to Loop I, astronomers have also detected also two other expanding bubbles nearby, called LOOP II and LOOP III. Over the last 5-10 Myr, the Solar System has been moving through the lower density region of the Local Bubble. As a result, Earth and its lifeforms have avoided dangerous flows of cosmic radiation and gas.

Some wisps of the Local Fluff's denser gas may already have blown into the Solar System earlier (possibly 30-60 kya) Such gas clouds can suppress the Solar Wind so that interstellar gas and dust enters the Solar System in quantities great enough to affect the Sun and life on Earth. At the moment, a powerful stellar wind from the young OB stellar associations of the Local Bubble's expanding neighbor, the Loop I Bubble, is pushing the Local Fluff aside. That expanding bubble, however, is also pushing other clouds of gas towards the Solar System. The neutral-gas-free tunnel extends some 250 pc toward the star Mirzam (Beta Canis Majoris), and the hot gas of the bubble extends at least 300 pc into the galactic halo. The Local Bubble may actually be part of a cylindrical cavity that pierces the galactic, dubbed the "Local Chimney" Energetic supernova explosions created fast-moving expanding bubbles of hot gas that collided with the surrounding cold gas of interstellar space, which in turn became compressed into thin shells. Eventually, these shells of cold gas met other expanding hot cavities and broke up to form small tunnels or pathways between the expanding voids. Such "hot chimneys" have been detected in other galaxies.

Some of the youngest stars found around the Local Chimney, where a compression wave some 30 Mya piled up a molecular cloud of gas around 200 pc across (Gould Belt). Gas, dust, young stars, and nebulae are concentrated in several star-forming regions that lie in a ring near the edge of the belt. These regions are known as the Orion Region, the Perseus OB2, Lacerta OB1, and the Scorpius-Centaurus Association. Intense radiation and the violent death of the first generation of stars in Gould's Belt have pushed most of the gas outwards to the edge of the belt, and supernova shockwaves have triggered the birth of most of the bright stars seen today from the Solar System. http://www.solstation.com/x-objects/chimney.htm

So, one of the reasons we see many bright stars today is that we are situated right at the edge of star-bearing clouds coupled to a large void. The compression of gas at the walls of this void sparked star formation just a few Myr ago - a wink of geological time. Even the low-density clouds towards which we rapidly move will present threat to terrestrial Life 20-50 kyr from now - and we are far away from the center of action, the spiral arms. What are these spiral arms? We see these arms because new OB stars that live only 10-100 Mya are being formed there en masse. A significant portion of these stars explode as supernovae, and the shocks and the stellar wind of the young stars compress the gas and lead to the formation of new stars; then the story repeats itself. There are two schools of thought about the arms. One is that these are density ways. Another is that the arms are formed by supernova chain reaction, i.e. self-propagating wave of star formation. Yet another idea is that

...the density waves may not be steady-state modes, there could be some driving system generating the waves. Many systems have been proposed from galactic bars and non-axisymmetric galactic halos to tidal disruption from companion galaxies. If waves are amplified efficiently by swinging, these disruptions could start very small and be amplified to viable spiral arms. Observations seem to back this theory. Quite a large percent of spirals appear to have either bar or bar-like structures at their cores or have had recent interactions with companion galaxies. http://casa.colorado.edu/~danforth/science/spiral/#SECTION0004001

The spiral arms and their configuration are not a fixture and we cannot confidently claim that the present situation of low density of interstellar medium around our solar system has been long in existence. The disk itself (the "thick disk") is likely to form due to slow digestion of satellite galaxies by the Milky Way. This process is still going on: there are two ongoing mergers (with the Sagittarius and Canis Major dwarf galaxies). The stars trapped by the merger stay in the thick disk, whereas cold gas collapses on the galactic plane forming thin disk and stimulates the formation of the spiral arms. The spiral arm configuration itself is changing.

Meanwhile, we are sitting just at the rim of a minor spur, Orion arm. One orbit of the Sun takes 225 Myr, so the Sun have completed 20 full rotations. Its circular orbit goes right through Perseus and Saggitarius arms. Orion arm itself might be a branch of Perseus arm. These arms are not very far - Perseus arm is just 6400 ly away (we orbit at 5 ly/ Myr). Given our poor knowledge of our present galactic backyard, it impossible to tell whether the solar system had been closer associated with the spiral arms in the distant past (0.5-15 Gya) and in which way. Having the familiar starry sky might be a relatively recent development in the history of solar system and it may not be a lasting one. I do not know any evidence suggesting that starry sky was observable from Earth before the emergence of plants. This is not a subject for mockery and conceit, but for understanding and research. It is important to know how the solar system interacted with its galactic bed throughout Earth's history. One day in not too distant future, such interaction can be the undoing of our present dominance on this planet.

Was the Sun always at the safe distance from the spiral arms? Was it always in the relatively low-density patches of the sky? Had it moved through the dense regions in the past and for how long? When and what effect did it have on Earth? The answers to all of these questions are unknown.

Why are there stars in our sky?

PS: The map of the Milky Way is on http://www.atlasoftheuniverse.com/milkyway.html

Et in Terra Pax

...And God made two great lights; the greater light to rule the day, and the lesser light to rule the night: he made the stars also. And God set them in the firmament of the heaven to give light upon the earth, And to rule over the day and over the night, and to divide the light from the darkness: and God saw that it was good. Gen. 1:16-18

In the last post we discussed the possibility that during its orbital motion around the galactic center the solar system may occasionally cross dense star-forming regions in the spiral arms of the Milky Way. One effect of such crossing is that the starlight is temporarily obscured; another - much more important - effect is the elevated flux of cosmic rays and the reduced protection of the Earth by the magnetic field of the Sun. The latter two effects may cause severe global cooling that would last until the dense region has been crossed. The current state of knowledge does not allow back extrapolation of the Sun’s orbit beyond 200-500 Myr into the past (the present spiral arm structure is expected to be this old), but the calculations suggest that there were four such crossings in the Phanaerozoic, around 80, 156, 310, and 446 Mya, that is roughly every 143 Myr. The last three arm crossings corresponded to the major Ice Ages with their peaks at 155, 319 and 437 Mya. Each such episode lasted 10-20 Myr. One of the many dangers lurking in the spiral arms are dense giant molecular clouds. If during the crossing the solar system gets inside one of such clouds, not only the starlight is dimmed, there is more serious trouble:
http://prola.aps.org/abstract/PRL/v89/i5/e051102
http://www.gsajournals.org/archive/1052-5173/13/7/pdf/i1052-5173-13-7-4.pdf
http://www.journals.uchicago.edu/doi/pdf/10.1086/430250

...The cosmic ray flux varies with a period of about 143 Mys, which correlates well with both the geological records of ice age epochs and the solar system's location relative to the spiral arms. Our current position should lead to cosmic ray fluxes about half of what we would receive in a major spiral arm. http://www.aip.org/pnu/2002/split/599-2.html

...The solar system encounters a dense (ca. 2000 atoms/cc) giant molecular cloud (GMC) with greatest probability every 140 My when the solar system crosses the galactic spiral arms where GMC’s are concentrated. Tropospheric dust loading during dense GMC encounters would lower radiative forcing by 8 W/m2 for ~200 kyr. This is close to the forcing required to convert the present climate to a global glaciation. The change in forcing upon entering a GMC is rapid enough that it cannot be compensated by silicate-weathering feedback. The authors conclude that in its 4.5 Gyr of existence, the solar system encountered ~4 high-density GMC’s, which could have triggered snowball earths, and ~15 lower-density (~1000 H atoms/cc) GMC’s capable of causing moderate ice ages. GRL 32, L03705

These moderate Ice Ages were bad enough, but it all pales in comparison with two or four glaciations that occurred at the end of Gryogenic Period of Neoproterozoic Era, 635 to 710 Mya, right before the beginning of Ediacaran Period of the new – our - era. Only after these glaciations completed, the multicellular life (metazoan animals and plants) took off. The worst time ever in the history of eukaryotic Life, around 700 Mya, roughly corresponds to the timing of spiral arm crossing, and it might be that the inevitable did happen: the solar system wandered dangerously close to the dense region of the spiral arm. During these two extreme glaciations, the whole planet might have frozen, with thin patches of clear-water refugia at the equator. The global and the equatorial temperatures dropped below -50 C and -20 C, respectively, and the sea ice was 1-5 km thick. The ocean became isolated from the atmosphere and became anoxic. The entire globe was in the condition of present day Antarctica. The ice reflected the sunlight reinforcing runaway cooling, and water vapor was freezing out, so the cloud cover disappeared further exacerbating the cooling. The glaciations ended only after sufficient amount of volcanic methane and CO2 accumulated to reintroduce the greenhouse effect. The ice melted, the ocean reoxygenated and the first marine animals have appeared. The new form of Life has passed its worst ordeal and it was that very ordeal that spurred the transition from unicel to multicellular life.

The snowball Earth was the combination of several things going wrong at the same time. The badly timed spiral arm crossing and the compression of heliosphere was only of them. The Earth continents happened to be at the tropical latitudes which increased the rate of rock weathering and caused efficient sinking of carbon.

...The end of Proterozoic era was characterized by formation of the supercontinent of Rodinia from about 1,000 to 800 Mya, the later breakup of this landmass and eventual reassembly into a different configuration by 550 Mya, during the final phase of the pan- African orogeny. At least two main phases of ice advance occurred, with glaciers apparently extending to the Equator at sea level. The first phase from 760 to 700 Mya is generally termed the Sturtian ice age, while the second, which occurred in the interval 620-580 Mya, is often termed the Marinoan ice age. The late Proterozoic also marked the first appearance of metazoans, perhaps as early as 700-1,000 Mya while the Varanger ice age was almost immediately followed by the time interval (Vendian) featuring the first fossil remains of multicelled animals, the Ediacaran fauna.
http://earth.unh.edu/esci762-862/Hyde%20et%20al%202000.pdf

...Around 760 Mya, Rhodinia started to split apart, forming a new ocean basin. As this rift tore open the ancient continent, it created new beachfront property as well as new coastal waters hospitable to plankton. Life bloomed in these regions. Rampant photosynthesis pulled billions of tons of CO2 out of the air, and this carbon got quickly buried on the continental shelves. Atmospheric concentrations of CO2 eventually dropped so low that Earth's greenhouse effect weakened. The planet could no longer hold heat, and the ocean started to freeze. Because the sun was about 7% dimmer than it is today, Earth was particularly susceptible to such a fate. Over 10 Myr, CO2 pouring out of volcanoes accumulated in the atmosphere until its concentration reached 350 times the present value. At that point, the supercharged greenhouse effect rapidly melted the ice and baked the Earth in temperatures far above those reached today. With so much CO2 in the atmosphere, rain turned highly acidic and eroded continental rocks. Calcium from these rocks would have washed into oceans and combined with abundant bicarbonate ions to form post-glacial carbonate layers around the globe. http://www.sciencenews.org/pages/sn_arc98/8_29_98/bob1.htm

The weathering of rocks produces bicarbonate that is calcified by cyanobacteria and algae. The cyanobacteria are prokaryotes; the algae are eukaryotes. Any drastic change in the efficiency of the calcification process, and more CO2 is sunk than can be replenished by volcanism and tectonics, so the planet begins to freeze. Another sink for C is organic carbon burial, which depends mainly on the availability of phosphates near river basins.

...Just before the time of the ice-age diamictites, the relative amount of carbon-13 dropped sharply. It declined slightly more after the glacial epoch. These isotopic excursions are enormous in comparison with any excursions in the preceding 1.2 Gya or in the Phanerozoic eon. The surplus of carbon-13 before the ice age reflects life in overdrive. Photosynthesizing organisms were pulling carbon-12 out of the water, and their bodies were getting covered over by a vast supply of sediments washing into the oceans. The tropical concentration of continental area may lead to more efficient burial of organic carbon through increased tropical river discharge. Efficient organic carbon burial sustained over tens of millions of years, required by the high carbon isotopic compositions of preglacial carbonate, may lead to the buildup of enormous quantities of methane, presumably in hydrate reservoirs. Moreover, the accumulation of methane in the atmosphere coupled with the response of silicate weathering to the additional greenhouse forcing can lead to a climate with methane as the major greenhouse gas. This situation is unstable because methane is not buffered by a large ocean reservoir like CO2, and so the collapse of the methane source may provide a trigger for the onset of a runaway ice-albedo feedback.
http://www.agu.org/journals/gc/gc0206/2001GC000219

For Gaia, the snowball Earth is a minor setback: anaerobes and chemolithotrophs replace aerobes and phototrophs as predominant ecotypes and the show goes on. For Eukaryotes, which are all aerobes, the snowball Earth was nearly the end of it. Phylogenetic trees suggest virtually unbranched stems up until the end of the snowball episode: the vast majority of eukaryote lineages went extinct.

How could anything like snowball Earth happen on a planet where the oxygenation was complete and the last glaciation of comparable magnitude happened 1 Gya before the snowball episode? Something was not working right, and this something was the rise of Eukaryotic phototrophs (aka “plants”) 2.1-1.7 Gya. The trouble was slowly brewing in the Mesoproterozoic, as the eukaryote phototrophs diversified, but the situation became critical at the end of Neoproterozoic when the algae became one of the dominant marine life forms and drastically increased organic carbon storage and sinking, depleting the atmosphere of the greenhouse gas. One of the reasons for the great success of the algae is that they seem to be the first ones who discovered the joys of sex (about 1.2 Mya) and radiated very early.
http://geolmag.geoscienceworld.org/cgi/content/abstract/140/4/397

Some people suggest that this radiation occurred earlier and was more extensive than commonly assumed, and they explain the snowball Earth by colonization of land by the early plants and fungi. This is controversial because the first fossil evidence suggests that the colonization began only at the end of the next glaciation period in the Ordovican. Yet the protein analysis has suggested that moss and vascular plants began to diverse 700 Mya.

...One of the first steps toward the colonization of land by eukaryotes may have been the formation of a lichen symbiosis, perhaps an endosymbiosis of a fungus and a cyanobacterium. Lichens and free-living cyanobacteria form a biological crust in harsh terrestrial environments today and may have done so in the Neoproterozoic. There is geochemical evidence for terrestrial ecosystems (prokaryotic) as early as 2.6 Gya and microfossil evidence 1.2-0.8 Gya. However, there is no undisputed fossil evidence of terrestrial eukaryotes until the Ordovician (480 to 460 Mya), when land plants and fungi first appear. If they arose earlier, as our data suggest, their potential effect on the environment and biota should be considered. One is a period of global glaciations and the other is a Neoproterozoic rise in oxygen. Fungi can enhance weathering, which in turn can lead to lower CO2 levels and global temperatures. In addition, the burial of terrestrial carbon, rich in decay-resistant compounds of land plants and less dependent on abundance of phosphorus, would further affect global climate. Either or both of these mechanisms could explain lower global temperatures (episodic or general) and a rise in O2 in the Neoproterozoic. http://www.sciencemag.org/cgi/content/full/293/5532/1129?ijkey=691c2e8aefccc1837a7b30baebb1612968d5add1

So the “plants,” either in their land or, more likely, marine incarnation had been involved, directly or indirectly, in snowballing the planet, and the cause for their disruptive effect was their appetite for CO2. Once thick ice covered most of the planet, the familiar cycle of seasons was disrupted; the climate was similar to the one presently found on Mars. The precipitation was extremely low, and ice particles at the ground were swept into the air to make aerosol haze that introduced antigreenhouse effect. A nontrivial consequence is that there was no hydrological cycle to remove the particulates from the air, so both volcanic and meteoritic haze persisted. We know that there were bombardment episodes during the glaciation because the ice collected Ir-rich dust that precipitated when the ice melted. Such bombardments are to be expected if the solar system went through the dense regions where the comet and asteroid reservoirs are disturbed. The "nuclear winters" would be of especially great severity on snowball Earth because there is no liquid water to rinse the atmosphere. Once again the atmospheric transparency began to decline and there were prolonged periods of dusty, icy atmosphere.

...At night during the summer a thin haze of ice crystals would have formed near the ground, which would have been colder than the overlying atmosphere. Much of this haze would have dissipated when the ground and adjacent air warmed during the day, but some crystals could have been carried aloft by weak convection. There would have been no towering cumulus clouds and very little wind. There would have been little that we would recognize as precipitation. The atmosphere was too dry. In winter, the ground would have been colder than the atmosphere both day and night. Midlatitude cyclones may have come and gone in the free atmosphere, but would have had little effect on the ground, isolated from the overlying atmosphere by the strong, stable, temperature inversion. There might have been thin clouds resembling cirrostratus in the upwelling regions of the cyclones, but again very little precipitation. This strange weather is a consequence of the aridity of the atmosphere and the solidity of the ocean. The ice-covered ocean does not transport heat to high latitudes and it does not store large amounts of heat in the summer for release during the winter. The longwave opacity of the dry atmosphere is low, so radiative coupling between ground and atmosphere is weak. In addition, latent heat plays no significant role in the transport of energy either vertically or horizontally. Ground temperatures therefore depend mainly on insolation, little affected by or affecting the circulation of the atmosphere overhead. http://gsa.confex.com/gsa/2001ESP/finalprogram/abstract_7029.htm

The end of the glaciation was nearly as much turmoil as the glaciation itself. Extremely strong winds (70 km/hr) and giant waves going down to 200-400 m swept the planet. There was massive release of methane from the gas hydrates and the likely aftermath was the hothouse. http://www.nature.com/nature/journal/v433/n7022/full/433115a.html

Why was this event unique in the last 500 Gya? Perhaps the combination of detrimental factors leading to it was unique, but there is also another reason: animals. The worms very efficiently recycle coastal sediment for organic carbon and make it difficult to bury carbon, preventing the plants from repeating their feat of getting all of us done in. It is still unclear what made the Proterozoic algae such efficient killing machines. I might be something as innocent as experimentation with biomineralization, for C storage and body protection. Carbonate mineralizing organisms typically begin lightly calcifying but rapidly become heavily encrusted as other organisms begin to graze on them. Curiously, both cyanobacteria cyanobacteria and algae began to encrust heavily around the time of the snowball earth and armored very heavily in the Vendian. The calcification by cyanobacteria began in earnest 1.4 Mya, which coincided with the period of eukaryotic radiation. This can be taken both as the evidence for predation and the need to store CO2 due to falling level of CO2 and rising levels of O2 in the atmosphere, due to more efficient photosynthesis by the eukaryotic algae. The more was stored, the less CO2 was to store and the CO2 levels began to plummet. http://www.cen.ulaval.ca/warwickvincent/PDFfiles/179.pdf

Bad luck and destabilizing effect of eukaryotic Life combined to push the latter close to the brink of extinction. It is not known how it managed to survive but it did and underwent a momentous change along the way. Following the snowball glaciation many things had to be started over, as the heavenly lights dimmed, the stars were obscured, the seasons de facto ended, and there were prolonged periods when the night and day could not be told apart. Never again such a comprehensive restart would be needed.

Imagine looking at the Earth long, long time ago. The yellow sun and the pale - still blue - dot with all of its inhabitants are inching towards the spiral arm of the Galaxy. The things are already critical on this dot, but its numerous inhabitants are too busy to be concerned with its fate, which is already sealed: all this world needs to become frozen wasteland is a small push that begins runaway cooling. And then this world is not observable any more, as it begins to traverse the dark cloud in front of it. You can no longer see what is going on, but you know that the pale blue dot is becoming the pale white dot, and most of its inhabitants are perishing without leaving a trace. You may also know that a tiny fraction of these eukaryotic survivors, the meek of their Proterozoic eon, will bring their form of Life to the greatest heights and inherit their world. You cannot deny your fallen creatures redemption, but hard must it be looking at the pale blue dot as it descends into the abyss.

Why are there plants?

...And God said, Let the earth bring forth grass, the herb yielding seed, and the fruit tree yielding fruit after his kind, whose seed is in itself, upon the earth: and it was so. Gen 1:11

Eukaryogenesis was the central event in the natural history of our planet. What were the first eukaryotes like? Some say that amoeba-like unicels capable of phagocytosis (engulfing solid particles and cells) are the most basal. The phagocytosis “explains” how mitochondria (alpha proteobacteria) have been integrated into their methanogenic archaebacterial host. Others say that fungi are a better model, as they demonstrate the largest range of metabolism: methylotrophy (living only on methanol), anaerobic mitochondria, ammonia fermentation, nitrite respiration, etc. They have seven distinct life cycles and seven patterns of sexuality, easily beating other eukaryotes in the sheer variety of functions. The fungi are osmotrophs rather than phagotrophs (no solids, just molecules); the importers that we have in our vacuoles they have outside, so they are more primitive in this respect. The prevalent wisdom is that the phagotrophy appeared either very early in the history of the Eukarya or was one of the defining features of their host ancestor, the “unicellular raptor.” The fungi might have branched before the phagotrophy developed, although it is hard to explain how they got their mitochondria. Due to the frequent horizontal gene transfer, it is very difficult to tell what came first and what came second. The protoeukaryon might have subsisted on fermentation and saprotrophy (digestion of decaying organic matter) in addition to predation on bacteria. There is an interesting theory that such raptors might have forced prokaryotes into various extreme environments and caused genomic reduction in them; according to this theory the original prokaryotes were MORE complex than the present ones and their present simplicity is the adaptive strategy to protoeukaryotic predation. In any case, the potential for predation was there from the start.

One of the earliest events in our history was the branching of the protoeukaryons into unikonts - the ancestors of amoebas and slime molds (Amoebozoa) and animals and fungi (Opisthokonta) - and Archaeplastida - the ancestors of phototrophs (plants and algae) due to the primary endosymbiosis event 1.6-2.1 Gya. This event involved the transformation of a cyanobacterium symbiont into an internal organelle, the plastid. In the course of this fusion, 90-95% of operational genes of the guest transferred to host’s nucleus, so most of the plastid proteins are synthesized in the host’s cytosol. This required the development of protein-import machinery of the type required for integration of mitochondria.
http://www-users.york.ac.uk/~jf510/fehling_et_al_2007.pdf

Some algae (Glaucocystophytes) still do not have well developed chloroplasts but harbor somewhat modified cyanobacteria. The next branching event in the phototroph subgroup occurred about 1.5 Gya, when red and green algae parted their ways. The latter are the ancestors of all land plants. The red and brown algae are the oldest eukaryotes found in the fossil record if one discounts the mysterious unicels called acritarchs, about which nothing is known except that they were abundant in Mesoproterozoic and resembled spores, eggs, or cysts of eukaryotes.
http://www.cimp.ulg.ac.be/Acritarchs.html

The first fossil evidence of the opisthokonts is much later, about 750 Mya. The history of red algae included the secondary endosymbiosis event about 1.3 Gya: the entire eukaryotic phototroph has been imbedded by another eukaryon, giving rise to Chromista. And that is not all: there are examples of tertiary endosymbiosis and plastid sequestration, both on temporal and permanent basis, between different types of unicels. It appears that many types of algae started as non-phototroph protists that switched to phototrophy relatively late in their history. The pertinent question is: why did they switch? Why are there so many types of eukaryotic phototrophs?

The answer seems to be self-evident: the phototrophy is a great way to live – all one needs for living is light, salts, and water. However, it comes with the terrible penalty: phototrophs are at the very bottom of the food chain. Switching to phototrophy is switching from being a hunter to being a prey. If the phototrophy is so great, why are there so relatively few modern examples of animals dependent on phototrophy? There are cnidarian and worm symbionts, there are snails that steal plastids from their cnidarian prey, and… that’s about it. The list is short, and these animals do not photosynthesize; they delegate this task to the algae. The sad truth about phototrophy is that it immediately puts one into harm’s way unless there are no predators. All evidence suggests that predation was what made eukaryons eukaryons, so one cannot explain the transition to phototrophy by the absence of predation. The protoeukaryons that merged with the cyanobacteria made devil’s bargain which is not easily understood, unlike is the case with their mitochondria. The algae and the cyanobacteria occupy the same niche. The advantage of having the cyanobacteria inside, therefore, is unobvious. Why is it better to have the cyanobacteria inside and regress to the bottom of the food chain than predate on these cyanobacteria and occupy a higher position in the chain? It is this devil’s bargain which is the division between the animals and plants: One group stubbornly refused the bargain. The other group made it time after time, in a variety of ways. It is not hard to imagine a world in which the photosynthesis would be entirely bacterial. After all, there are no anaerobic eukaryotic phototrophs, although nothing prevents such a possibility, especially in the view of probable hydrogenosome origin of the mitochondria and the late switch to aeroby. Not all possibilities may realize, because any advantage, however great it may seem, comes with a disadvantage. In the case of phototrophy the advantage was considerable but the disadvantage was also great. Our line (Metazoa) consistently refused to become the source of food for everyone else; the plants wanted nothing else. Very few unicellular eukaryotes (e.g. dinoflagellates) have it both ways: they can both photosynthesize and hunt. Interestingly, it is this group, rather than the exclusive photosynthetic specialists, that later became symbionts with animals.

So the question can be reformulated in the following way: why did the hunter voluntarily turn itself into a prey? A possible answer is that the primary endosymbiosis was less the act of seeking cheap food, but the solution to a more pressing problem. Phototrophic eukaryotes emerged when the ocean, unlike the atmosphere, was relatively anoxic except for the thin surface layer and the predominant form of marine bacterial life was sulfate reducers, as the oxygen had first to oxidize sulfide in the sea water. This situation persisted until 800-600 Mya, as the oxic shift in the deep ocean was slow. Our mitochondria still have the limited ability to cope with the anoxia and high sulfide concentration, which might be biochemical relics of these sorry beginnings.
http://www.nature.com/nature/journal/v423/n6940/full/nature01651.html
http://www.sciencemag.org/cgi/content/abstract/297/5584/1137

The protoeukaryons lived at the margins of this oxygen-starved world, under great anoxic stress, where both the cyanobacterial food and oxygen were scarce. Another scarce commodity was nitrogen. N fixation is practiced by the cyanobacteria, but it requires a lot of energy and another scarce commodity – molibdenum – for N-fixing enzymes, nitrogenases. Mo (as well as Fe) should have been especially precious in sulfidic ocean. The nitrogenases are inhibited by O2 and thus require detoxification; few cyanobacteria mastered the art of N fixation; most of them have to rely on the external source. The scarcity of N in the ocean is the basis for coral symbiosis: the animal provides nitrogen, the zooxanthellae provide carbohydrates and oxygen (so normoxia can be maintained even in anoxic water, e.g. in sea anemones). Perhaps this kind of barter also led to eukaryotic phototrophy: cyanobacterial O2 was used to provide the oxidizer for mitochondria whereas phagocytosis was used to solve the problem of N scarcity through recycling of organic matter, to build more plastids.

While we know that there were non-phototroph eukaryotes in the anoxic ocean, we do not know whether these eukaryotes were exclusive aerobes. Rather, like some fungi, they may have relied on H2-producing fermentation and/or having anaerobic mitochondria. The oxygen for aerobic mitochondria in the phototrophs was produced locally, in the plastids. Only when these phototrophs managed to produce enough oxygen to oxygenate the entire ocean, only then switching to wholly aerobic way of life made good sense. Before that, having efficient aerobic metabolism required making one’s own oxygen, which may explain the temptation to become a plant, no matter what cost.

So the snowball earth event examined in the previous post might have been the inevitable consequence of eukaryogenesis. To take maximum metabolical advantage of their mitochondrion symbionts, the eukaryons needed oxygen, but the ocean was largely anoxic and so they needed to produce it locally. Some of them sacrificed their place in the food chain and acquired plastids from cyanobacterial symbionts. Initially, it might have paid off because their predators relied on anaerobic metabolism and were no match to more energetically efficient aerobes. However, as the greater number of eukaryotes became superefficient phototrophs they set their own demise, in two related ways. First, they removed too much carbon and initiated global cooling of unprecedented magnitude, which nearly wiped out eukaryote Life. Second, they oxygenated deep ocean and so made it possible for other eukaryotes to switch to aeroby without the need for making their own oxygen. Once that happened, grazing became extremely efficient way of predation and the floral life was never the same. Luckily for us, the global cooling triggered by the photosynthetic frenzy occurred when the transition from anaeroby to aeroby was still incomplete. Were it complete, the plants would succeed in elimination of their predators: us. As happened instead, the unikonts pulled through, switched to aeroby and some of them became animals and checked the out-of-control C sinking for good. No more the plants had the ability to get rid of the rest of the Eukarya. Their best bet was to find themselves a new niche: the land. And that is what happened next.

Why are there plants?

PS: Nice reviews of plastid evolution and the problems of anoxic world can be found in this collective volume, Microbial Phylogeny and Evolution

Exodus of the chosen

...And the earth brought forth grass, and herb yielding seed after his kind, and the tree yielding fruit, whose seed was in itself, after his kind: and God saw that it was good. Gen 1:12

Colonization of land by plants is told as a heroic saga of brave green algae that became multicellular and single handedly “brought forth herb, yielding seed after his kind” preparing the colonization of land by animals. The real story might have been lower on heroics, but higher on drama: it is actually highly doubtful that multicellular green algae have colonized the land. Rather, they might have colonized an organism that already colonized land by means of brutal oppression of these algae.

If this sounds bizarre, then it is. Everything about the evolution of land plants is bizarre. For starters, there are no truly multicellular (rather than colonial and filamentous) aquatic green algae, whereas there are many types of highly developed multicellular red and brown algae. There are nominally multicellular algae (sea lettuces) but they display almost no cell specialization; these are, in fact, semicolonial organisms. So we have to believe that the green algae, one of the oldest eukaryotes, transitioned to multicellularity only once and very late in their history, in the form that was ancestral to land plants. On the other hand, one cannot say that the green algae have been unaware of the charms of multicellularity. These algae form a symbiotic relationship with multicellular fungi, in lichens. This symbiosis is not mutualistic: the algae are brutally exploited by the fungus as the source of food. The question one can ask is the following: were the ancestors of the green algae that “brought forth grass” free living or symbiotic? There is little doubt that lichens came out of water first, as they are still first to colonize marginal environments, and land 400-700 Mya was, to put it mildly, a marginal environment. “Colonization of land” by primitive plants sounds an unlikely proposition. Even today, plants cannot manage on their own. Evolutionary success on the par with animals has long eluded them.

The interesting thing about land plants is their relatively low diversity, once the flowering plants (235k species) are excluded. There are only 550 species of conifers; the most populous genera are ferns (10k species) and mosses (12k). By contrast, there are 1.5M species of fungi and 2-10M species of insects. The first evidence of (moss-like) land plants is from the middle Silurian, about 425 Mya; before that only spores and cuticles (waxy layers) are found. For all we know, these spores may be from freshwater plants. So, even 150 Myr after the glaciation and tens of millions years after the explosion of animal diversity the plants barely made it onto land. Once on land, their diversification has been stagnating until 80-90 Mya, when the flowering plants appeared (nobody knows how). The genome sizes of nonflowering plants are smaller than those of alga and protists, while flowering plants easily beat mammals by a factor of 10. Still, crustaceans, lungfish, and salamanders have larger genomes than flowering plants.

The standard view is that the colonization of land by plants was extremely slow because it required many adaptations: the stomata (pores that open and close when necessary), supporting tissues (xylem vessels: wall thickenings), thick spore coats to avoid desiccation, vascular structures, etc. Only when these critical adaptations amassed, the radiation of plants began. One can say the same thing about colonization of land by animals. Yet it was rapid and carried out independently by several taxa.

The problem with the green alga origin of plants is that modern plants are not just plants. Land plants critically depend on fungi. First, about 80% of higher land plants wholly rely on mycorrhizal fungi for delivery of nutrients from soil, and this association is at least 460 Myr old. Second, nearly all plants harbor endophytic fungi whose alkaloids act as toxins for herbivores; the endophytes also increase resistance to draught and competition. Third, the plants have to grow on soil. The first plants had no roots and it is not clear how they managed to collect nutrients from the primitive soil. Only fungi have biochemical tools required for breaking up dead plants (especially, lignin). Without this process new plants cannot grow. So land “plants” are all about plant-fungi interactions. The heterodox view that was suggested some time ago by Atsatt, is that that land plants have lichenized fungal rather than free living green algal ancestry.

...In lichens, the photosynthetic cells are found in a defined band, where they are intimately joined to the hypha of the fungi, for the exchange of nutrients. These cells belong, in the majority of lichens, to green algae of the family Chlorophyta. However, in 10% of cases, these partners are blue algae, or cyanobacteria, of the family Cyanophyta. There exist, as well, a small percentage of lichens that contain both types of algae. The fact that they can have more than one type of photosynthetic partner demonstrates that this association probably evolved independently, and on more than one occasion, during the history of life. Recent research shows that the relationship between algae and fungi is much more complex than it appears at first sight. Evidence exists that the algae, in spite of receiving water and minerals from time to time, are effectively exploited by the fungi which use more than 50% of the nutrient produced by them. In this sense, this relationship appears to be more one of parasitism than of symbiosis, in which the fungi seem to "cultivate" their partners, obliging them to produce nutrient through photosynthesis. It is for this reason that the alga in a partnership is capable of living its own life and grows more quickly when this happens, which is not the case for the fungus. In this way, it (the fungus) should be considered the dominant partner, which survives by keeping the alga captive. In really difficult circumstances, the fungus can kill or control some the algal cells, thus confirming its domination. http://www.naturlink.pt/canais/Artigo.asp?iArtigo=2977&iLingua=2

The fungus provides moist environment (“hypersea”) and minerals to the green algae it hosts and cultivates, allowing the algae to expand their habitat. That said, the algae do not need this fungal gift because all that they need is abundantly present in the ocean. The terrestrial fungi dragged their symbionts out on dry land without asking them whether they prefer the sea, which they very much do. Lichens are heaven for fungus and hell for the algae. However, for the chosen ones of them, the slavery ended by the most unusual exodus story. Atsatt suggests that at some point the exploitative relationship turned inside-out, and that was the origin of plants. At least three scenarios are possible. First, the algal guest could have become the dominant partner. Second, the fungus could have learned the art of photosynthesis through horizontal gene transfer from its symbiont. Third, the lichens might have been colonized (parasitized) by a new, colonial or multicellular, type of green algae that got a free ride from the already established symbiotic interaction and turned it to its own complete advantage. Whatever happened, it sealed the future of land forever.

...Vascular plants are far more than simple extensions of green algae. They are comparatively too complex, diversified too quickly, and contain numerous fungus-like cells. A lichenized ancestor to vascular plants may be the alternative. The ancestral lichenization resulted in a "reverse-phase lichen" with a dominant algal component containing an endophytic, mineral scavenging fungus similar to extant mycorrhizal associations. Nuclear fusions between the fungal and algal cells resulted in hybrid nuclei containing the traits of both parents. In true synergistic fashion, this dual genome gave rise to a plant body composed of a mosaic of alga-like photosynthetic cells interspersed with specialized fungus-like cells. Several types of cells and tissues in vascular plants resemble fungal hyphae, including pollen tubes, vascular tissue, laticifers, and haustoria. Pollen tubes not only resemble the growth of fungal hyphae, but in Pinus, cycads, and Ginkgo they are branched and actually absorb nutrients from the "host's" megasporangium. The latex-producing laticifers found in many members of the Euphorbiaceae, Asclepiadaceae and other dicotyledonous families are very similar to fungal hyphae. Nonarticulated laticifers are elongate, multinucleate cellular tubes that grow throughout the plant body of these families. Some endophytic parasitic flowering plants, such as certain dwarf mistletoes and the remarkable Pilostyles thurberi of the Colorado Desert, live completely within the host tissues and only emerge from their host to produce flowers. The vascular tissue of these endoparasites literally permeate the host tissues and truly resemble fungal hyphae. The absorptive haustorial organs of many parasitic flowering plants which penetrate the host tissue are also very reminiscent of fungal hyphae.

...aquatic fungi might have evolved into a terrestrial form about 1.3 Gya. These early fungal forms were actually lichens because they formed a symbiotic relationship with primitive aquatic green algae. The early land surface of the Earth at this time contained numerous rock lichens. The bright pigments served to reduce the harmful effects of ultraviolet radiation in a primitive atmosphere. Evidence from mutation rates in 119 genes common to living fungi and plants, indicates that ancient land plants appeared about 700 Mya. http://waynesword.palomar.edu/pljan98.htm

...Despite their distant phylogenetic origins, fungi and plants have similar biochemistry's that may reflect the fact that both coevolved. Selection for molecular cross-talk with cyanobacteria hosts, and later plastids, may have conserved many ancestral sequences in early fungus lineages. Such preadaptation may have fostered plastid-incorporation experiments by terrestrial fungi. Fungus relatives (metazoa) cannot convert either the nitrogen of nitrate or the sulfur of sulfate into organic compounds, whereas fungi can not only assimilate nitrogen and sulfate, they share similar pathways with both cyanobacteria and plants. In plants it is the plastid that contains the key enzymes nitrite reductase, glutamine synthetase and glutamate synthetase, as well as all of the enzymes involved in sulfate reduction. Sporopollenin, the resistant material characterizing the outer walls of spores and pollen grains, occurs in only two eukaryotic groups: green plastid-containing organisms and fungi. Coumarins, best known as plant defense compounds, are also produced by fungi. In plants the key coumarin biosynthetic enzyme is associated with chloroplast membranes. The biosynthesis of rubber by fungi and modified plant plastids is particularly compelling. Rubber (cis-1,4-polyisoprene) may account for up to 6% of the dry weight of some basidiomycete fungi. Highly modified plastids called Frey-Wyssling complexes are thought to be involved in plant rubber. http://www.mycosomes.info

Are land plants “photosynthetic fungi?” What was the real story of land colonization?

PS: PR Atsatt Fungi & the Origin of Land Plants

Interlude 3. The Promise of Redemption

Before embarking on the part of the narrative that involves the creation of animals and humans, I have to put this story in a broader context. I do not aim at retelling textbooks on evolutionary biology and paleontology. Such books do excellent job in conveying the current reconstruction of the past. However, these books do not offer much in a way of explaining as to why the natural history of our planet took its particular form and where it all goes. This omission greatly dilutes the impact of the message. Yet I do not see how this situation can be mended, because such explanations do not belong to science. I do not know where these explanations belong to: philosophy? religion? fiction? What I do know is that without such explanations our knowledge is dead on arrival. When one is asked, "What animals are for?" - it helps not retorting that such a question does not belong to science; the question does not go away, and people who asked it are interested in truth rather than what part of this truth we agree to call science. Where I cannot rely on the power of science, I have to rely on the power of imagination, the power of inspiration, and the power of tradition. What follows is one person’s vision of this broader context. It is up to you what to make of this vision. I need the framework to continue this story, as I needed the framework to begin it. It cannot hang in the air.

Let us recapitulate the story. In less than 2 Gyr since the arrival of prokaryotic Life on our planet, it succeeded in transforming the inhospitable Terra into Gayan paradise. The Eden abruptly ended 1.5-2 Gya with the onset of eukaryogenesis. The seed of the trouble has been sown from the beginning. The prokaryotic Life always had the potential for producing the form of Life that, unlike itself, is based on the autonomous individual existence. On Earth, this potential was realized through the occurrence of eukaryogenesis, and this pivotal event in Earth’s history (that I, following Christian tradition, call “The Fall of Nature”) fully defined the character of terrestrial Life: the strife, the struggle for survival, predation, parasitism, and death. While the eukaryotic Life, like any Life, is a thing of great beauty and sophistication, it is also grave danger. A form of Life that is based on individual existence has the intrinsic potential of producing ever more powerful individuals, and this line of development, if pursued unchecked to its end, leads to the eventual appearance of the creature that, for lack of inventiveness, I will call Satan. I leave it to the others to decide how close is this creature to the biblical Prince of the World. Satan, far from being the worthy adversary of the creator and the incarnation of evil, is the logical endpoint in the evolution of the self. It only takes to the extreme what is inherent in individuality and complements it with the developed ability to realize its vision of good: the proliferation of the form of existence that is based on the self. It does not occur to Satan that this process also recreates and spreads the misery and strife that are inherent in the very nature of individuality and that Satan's interaction with the rest of the creation has enduring and corrupting effect. From the standpoint of Satan, the increase of its dominion is benign and desirable; other forms of Life are primitive and needing improvement. One can find abundant examples of this mode of thinking in the heroic sagas of exploration and colonization of space furnished by our sci-fi writers. The descriptions of other worlds can be exotic and fantastic; the humans and aliens come out instantly recognizable. What is omitted from such stories is that the contact or, worse, occupation of other worlds by individuals, regardless of their advancement, intentions, and priorities, irreversibly corrupts these worlds by tempting such worlds to fall. Satan does not corrupt through the display of evil; it corrupts through its very existence, its example, and its good. If the sci-fi visions of our “manifest destiny” were even partly true, we would be Satan. Fortunately, it is not going to happen. That is not our future.

Yes, the terrestrial Life has unrealized potential of becoming Satan, and truth is that we are already in its Princely dominion. Our world fell, and it may fall completely and absolutely by exporting its malignance universally. All habitable worlds come to an end, and this pushes Life to spread further out. Spreading of our Life would have dramatic repercussions for the entire creation, and it has to be prevented. This preventive, corrective action is the Redemption of our world. I cannot think of a more proper word. Life is of absolute value, even when it goes astray. The harm cannot be undone, but fallen worlds can be saved from becoming Satan through their transformation. Gaya might have been the fruit of such labors in the distant past. Earth is to be redeemed in the future. This Redemption is going on right now, and we are part of it. It started right after the Fall and it will continue when we will be dust.

We call this Redemption evolution. Its purpose is changing the character of eukaryotic Life. I cannot tell what form Life will eventually assume, but it will not duplicate Gaya in any other respect than the complete remission of the self. An entirely new way of such transformation is being tried here on this planet; it is as unique as the terrestrial Life itself. We (humans) are part of the Redemption, but neither are we its purpose nor its beneficiary. The creation will not stop with us. There will be many days of creation ahead, each one as good as the previous ones, and what will become of Life will bear as much resemblance to us as we have to the proto-eukaryotic chimera whose emergence sealed our fate. Our only importance in this transformation is that without us it cannot occur. We are the link in the chain of events connecting the fallen and the redeemed Life. That and only that makes us special. I do not think that is small.

The regrettable but essential feature of the Redemption is that only the elect will inherit the Kingdom of Heaven. On our planet, these elect are called animals, and the chain that I envision is none other than the lineage connecting us to the Urmetazoan ancestor that appeared 900 Mya. I cannot tell why this particular form of eukaryotic organization has been chosen over the others for the purpose of Redemption. The metazoans looked like the certain dead end, as the concentration of oxygen back then was prohibitively low for them to flourish. What changed everything was the evolution of super efficient eukaryotic phototrophs which oxygenated the oceans, making our way of life possible, but not before inducing the global catastrophe that nearly terminated all of the eukaryotic Life: the snowball Earth. The great thaw that ensued had finished the necessary preparations to our explosive radiation: finally, the concentration of oxygen in the seawater rose sufficiently high to make our particular adaptations advantageous. We would not be here without this hellish episode. Many of eumetazoan adaptations, including the sophisticated respiration system, have likely originated in the need to survive the anoxia during the glaciation epoch. The greatest value of animals, however, was not in their innovative metabolisms; it was their organization. The metazoans achieved the feat that selected them as harbingers of the Redemption: the individual eukaryotic cells fused into the new entity: differentiated, multicellular organism of unparalleled adaptability and plasticity. The selfishness of the cell was subordinated to the new type of the self, and that new self was the first step towards the salvation.

Why are there animals?

...And God said, Let the waters bring forth abundantly the moving creature that hath life, and fowl that may fly above the earth in the open firmament of heaven. And God created great whales [sea monsters], and every living creature that moveth, which the waters brought forth abundantly, after their kind, and every winged fowl after his kind: and God saw that it was good. And God blessed them, saying, Be fruitful, and multiply, and fill the waters in the seas, and let fowl multiply in the earth. Gen. 1:20-22

This verse refers to the explosive radiation of multicellular animals (Eumetazoa) in the Cambrian, about 540 Mya: in a short period of time, possibly as brief as 10-30 Myr, all of the present animal phyla came into existence. This radiation was so rapid that molecular clocks that are commonly used in cladistic analyses are unable to resolve the order of succession. Many of the extinct Cambrian creatures look monstrous to us because their lineages became extinct, and their extravagant body plans might have been the reason. The supreme act of biological creativity that was the Cambrian explosion has never been surpassed, and it is unprecedented in the natural history of our planet. There were animal-like creatures before the Cambrian, in the Vendian period, but the Vendozoa, which are believed to be cnidarians (jellies) without their stinging cells, disappeared without trace. There is an unorthodox opinion that these Vendobiota were not animals, but rather marine lichens that supported their mineral intakes by endocytosis, or other phototrophic or chemolithotrophic symbionts. These Vendozoa and a few fossils that look like modern worms are the only traces of animal life before the explosion.

What caused this sudden eruption of animal diversity? That is not known. Several causes or the convergence of such causes have been suggested. For the first time in Earth’s history, the concentration of oxygen in the sea was sufficient to maintain active respiratory metabolism. Other factors may have compounded this opportunity: the invention of the eyesight and biomineralization (that was made possible by changes in ocean chemistry), and the appearance of developmental toolbox, such as Hox genes, that translated minor genetic variations into radically different body plans. All of these inventions were slow in coming, but these fortuitously converged around the same time, allowing the staggering variety of predative and evasive strategies to appear simultaneously. The fortunate possessors of these traits rapidly occupied all of the niches of marine life, replacing nearly everything that existed heretofore. In the following 520 Myr, no new radical inventions and/or drastic changes were needed: the evolution of the existing animal lineages was sufficiently rapid for at least a subset of the species to thrive under ever changing conditions and reoccupy the niches emptied by inevitable extinctions. In other words, the animals rule the Earth because they are the most adaptive and rapidly evolving branch of eukaryotic Life, and their spectacular diversity makes them nearly invincible, as a kingdom of Life, to the travails and tribulations of the earthly existence. Short of the return of global anoxia or equally catastrophic event, this rule will expand and continue, and the diversity of Animalia will increase further. Over the last 300 Myr this increase was nearly exponential. Animals are the most diverse and the fittest of the autonomous selves furnished by the unfolding miracle of evolution.

This success was not apparent before the Cryogenian, when the oceans were largely anoxic. The oxygenation that occurred right before the glaciation was caused by the explosion of eukaryotic phototrophs which depleted carbon dioxide and brought both this glaciation and temporary anoxia, undermining the future of the Metazoa. This future remained uncertain even 50 Myr before the Cambrian explosion and the very survival of our ancestors during the glaciation and post-glaciation hotbath is a puzzler. Somehow, they pulled through; my opinion is that the ones that made it were symbiotic with the algae. One can ask a more difficult question about the evolution of multicellularity, the emergence of two sexes, and germ-soma division that were major steps towards the animals, as these features have no apparent advantage for their survival and fitness and thereby poorly fit into the Darwinian doctrine. The sponges (Porifera) are as perfect a multicellular organism as the jellies, but their cells are totimpotent and the sponges have infinite regenerative power, being capable of regrowth from a single body cell. Hydras (small freshwater cnidarinas) are capable of permanent rejuvenation: all of the cells of their bodies are replaced once in 10-20 days; unless the hydra is physically destroyed, it is immortal; it also has the ability to grow back out of a clump of a few cells. I am hard pressed to point out survival advantages that mortal animals have over their immortal kin. The great increase in the fertility rates and diversity of the mortals compensate for the high rate of attrition; the immortals do not need these adaptations. If the survival rates are extremely high, differential survival can not be the driving force for evolution, especially for the transition from immortality to mortality. Furthermore, the bizarre arrangement where there is an immortal germ line and mortal, expendable soma - in which many of the body cells die during the normal operation, more die during the development and aging stages, and all of them die eventually – does not seem to aim either at the “survival” of the organism as a whole or its fitness. It is a terrible predicament for most of the cells, and it is not clear how did this organization appear as a result of slowly accumulating advantages for individual cells. These cells have denied their autonomous existence, their selves – for what? The advantages of a colony are obvious, but the advantages of the hierarchical organization patterned on the most oppressive tyranny do not readily reveal themselves.

The origin of eumetazoan multicellularity is the question that I believe to be most essential for answering the title question. I am not alone in such thinking.

...Our understanding of life is being transformed by the realization that evolution occurs not only through the standard processes operating within populations, but also during evolutionary transitions in individuality, when groups of individuals become so integrated that they evolve into new higher-level individuals. Indeed, the major landmarks in the diversification of life and the hierarchical organization of the living world are consequences of a series of evolutionary transitions: from cells to multicellular organisms, from asexual to sexual populations, and from solitary to social organisms. Such transitions require the reorganization of fitness, by which we mean the transfer of fitness from the old lower-level individual to the new higher level, and the specialization of lower-level units in fitness components of the new higher-level individual. It is a major challenge to understand why and how the basic features of an evolutionary individual, such as fitness heritability, indivisibility, and evolvability, shift their reference from the old level to the new level. The evolution of multicellular organisms is the premier example of the integration of lower-level individuals (cells) into a new higher-level individual. How does a cell group evolve into a multicellular individual? Although kinship has long been appreciated as a necessary precondition for the transition to multicellularity, there are colonial species with high degrees of kinship that have not evolved true individuality. The evolution of multicellular individuals involved the formation of cell groups, the increase of cooperation within the groups, the evolution of conflict mediators to protect the group against cheaters, the increase in group size, the specialization of cells in essential fitness components of the group, and the spatial organization of these specialized cell types. Multicellularity arose in the myxobacteria some 2 Gya, in the animals and plants, between 600 and 1000 Mya. Studying the factors involved in these ancient origins of multicellularity is difficult because the events are obscured by hundreds of millions of years of subsequent evolution.

...There are several hypotheses for the evolution of cell specialization. The first involves the evolution of cooperation (versus defection). To cooperate, cells presumably must specialize at particular behaviors and functions. The evolution of costly forms of cooperation, altruism, is fundamental to evolutionary transitions, because altruism exports fitness from a lower level (the costs of altruism) to a higher level (the benefits of altruism). The evolution of cooperation sets the stage for defection, and this leads to a second kind of hypothesis for the evolution of specialized cells involving conflict mediation. If the opportunities for defectors can be mediated, enhanced cooperativity of cells will result in more harmonious functioning of the group. A variety of features of multicellular organisms can be understood as "conflict mediators," that is, adaptations to reduce conflict and increase cooperation among cells: high kinship as a result of development from a single cell, lowered mutation rate as a result of a nucleus, self-policing of selfish cells by the immune system, parental control of cell phenotype, programmed cell death of cells depending on signals received by neighboring cells, determinate body size, and early germ soma separation. These different kinds of conflict mediators require different specialized cell types. The third hypothesis for specialization involves the advantages of division of labor and the synergism that may result when cells specialize in complementary behaviors and functions. The most basic division of labor in organisms is between reproductive and vegetative or survival-enhancing functions.
http://www.pnas.org/cgi/content/full/104/suppl_1/8613

You can read these and other speculations on the origin of multicellularity and germ-soma division, but the unfortunate fact is that the only recent (ca. 70 Myr) example of developing multicellularity (in green Volvox algae) is quite different from the eumetazoan multicellularity, as any cell in these colonial algae can potentially become a germ cell and so there remains hope of not paying the ultimate price for one's altruism. Furthermore, it is not hard to imagine viable alternatives to irreversible differentiation, germ-soma division, etc. in animals and some of these alternatives have been around for millions of years and proved their worth. There seem to be no "reason" for selection towards the particular form of multicellularity occurring in animals in the familiar terms of fitness, survival, conflict resolution, and specialization. As in the case with other major evolutionary transitions, when theoretical insight is particularly needed, our theories appear to be impotent. Something important is obviously missing, and that something may be the key to the evolutionary process. I do not pretend that I know what is missing, but I can offer my own speculations. I believe that the missing part is the formulation of the goal and the direction of eukaryotic evolution. By postulating this goal and this direction, one gains better understanding of the nature and inevitability of these major transitions. On the down side, it is impossible to prove that the evolution does have such goals and direction. It is also impossible to prove that evolution is driven by Darwinian selection alone. The evolution of individuality could be the complementing principle to the evolution of the body.

The animals became the predominant form of eukaryotic Life only when the present cellular organization took hold, when the last vestiges of cellular selfishness were extinguished and the cells became totally interdependent. The animal is a bold step away from the autonomy of unicel existence towards integrated living that is typical of prokaryotic kingdom, albeit on a smaller scale. The cells remain united into an individual, a self, but these cells fully relinquished their autonomy. From the standpoint of an individual cell, it is a loss, but from the standpoint of the organism, it is a gain. However, the organism is a collection of its cells; there is no physical “self” in it other than these cells and the way they arrange. This trivial observation is important, because it contrasts with the typical way we perceive ourselves. Nobody would say that the loss of somatic cells (say, by amputation of a limb) or germ cells (by castration) terminates the self. Killing neurons may cause death, but this does not mean that such cells are the repository of the self: lower animals (e.g., flat worms) can lose a large number of such cells and regenerate. Nobody would say that a planaria worm which is cut into half has lost its self. The loss of the cellular selfhood is obvious, but the repository of individuality isn’t, as the new type of self is the potential ability to function collectively. Until this ability remains, even as remote possibility, the self is preserved. Apart from this ability there is no self, but this ability is not the physical fact of the world. It is apparent only to other animals. It completely eludes the bacteria and viruses that parasitize on us; for them we are the collection of our cells.

Sometimes one hears that there is no mystery here: just look at the machines. They are functional assemblies of differentiated components, like us. The problem there is that the machines are designed and built by animals (us) and recognized as such also by animals (us) who treat them in much the same way we treat other animals. One needs an animal to recognize a man-made machine as a machine. A mountain or a galaxy can have any number of complex, integrated, interlocked parts and may also have the ability to divide and bring forth new mountains, galaxies, etc., but these objects will be sternly denied to have “selves” or regarded as living. So having the self of our type implies not only the collective survival but the ability to recognize another such assembly as a “self.” It isn’t just a new way of organization of living matter; it is a new concept of individuality. Objects that do not conform to this concept do not have selves.

That is why I consider the appearance of metazoans as the first step towards what I call the Redemption: the pathway from eukaryotic Fall and the subsequent atomization of terrestrial Life towards its new integration, on novel terms, into a self-less entity; this integration might be crucial for the long term survival and proliferation of our form of Life. After 600 Myr since the Fall, the cellular self has been eliminated and supplanted with the organismal self. The organisms still have individuality, but this self is more ideal than real, and it is meaningful only as far as it is recognized as such by other individuals. The new selves continue to be at war with each other and their existence is even more macabre than that of their protist ancestors, as the organism has more to lose than opisthokont unicels, but the cellular merger and the specific way in which it occurred, as opposed to the alternatives briefly mentioned above, betray the promise and the general direction of evolution. The first step towards a neo-Gayan world has been accomplished, albeit at a terrible price and by terrible means. It took a while to finesse the merger, but it was over by the Cambrian, and starting from that time the center of action has moved towards the next step: integrating the animal selves into a new form of Life. The diversity, evolvability, and the supreme adaptability of animals are the means of achieving this goal. These qualities ensure that among animals a new order of organization will eventually appear. Just as out of many species of protists only one lineage, Choanoflagellates, proved capable of achieving the transition to animals, and only after a series of major transitions, out of billions of animal species that ever existed only a few lineages are potentially capable of the next transition; perhaps only one species. This species can occur only through the maintenance of great diversity, because the emergence of the quality that is required for the transition is a probabilistic event. Yet the goal and the means of its achievement have been determined at the outset. The advantages of the integration are so high that once the transformation is achieved, it would be locked forever, similarly to the transition from the colonial protists to animals. It does not matter what animal in what lineage achieves this quality first. The trick is to have as many species in as many habitats as possible and give the evolutionary process sufficient time. That is why animals appeared suddenly and in such variety shortly after the environmental conditions for their precarious existence were met. Creation by evolution takes time, and there is little time to spare.

The integration does not mean that the Redemption will require fundamental changes in the animal nature, as it did not bring such changes in the nature of eukaryotic cells during their merger. There are rudimental forms of this integration apparent in several branches of animal life: social insects, polyp corals, complex ecosystems, etc. These are success stories, but these modes of integration are short of the desired goal. A new quality is required. These previous attempts – just like the hydras and the sponges – are the reminders of the creativity of evolution randomly striving towards its elusive goal. The particular path is less important than this quality itself, and it is impossible to rely on a random process and expect fully predictable outcome. I believe that this sought quality is a certain level of intelligence. Of course, the intelligence is the universal feature of eukaryotic Life, and I would not deny it even to slime molds. The animals have to have at least as much intelligence as needed to recognize other objects as animals and that requires abstraction. It is not intelligence per se that is being sought. It is the intelligence that is capable of a new concept of the self.

It is ironic that the animal that stepped on the path towards this transition has descended from mammals. Even 70 Mya, the mammals appeared to be the dead end of evolution rightfully destined for extinction. If there is any truth in the saying that the meek shall inherit the Earth, it has been borne out in our case, time after time. But that is a different story.

Why are there animals?

Why are we land animals?

...And God said, Let the earth bring forth living creatures according to their kinds: cattle and creeping things and beasts of the earth according to their kinds. And it was so. And God made the beasts of the earth according to their kinds and the cattle according to their kinds, and everything that creeps upon the ground according to its kind. And God saw that it was good. Gen 1:24-25

There are several reasons for the existence of land animals. All of these have to do with the survival of Animalia. The main reason is the vulnerability of our oceans to anoxia. Most of the oxygen that is generated by water-splitting phototrophs resides in the atmosphere, and every time the atmosphere is decoupled from the oceans the latter become anoxic, which results in mass extinctions of marine life. There is a repeated pattern to such extinctions and prudence requires hedging one’s bets by having a reservoir of animal life that can survive such calamities and repopulate the planet after the devastation.

The second equally important reason is keeping vascular plants in check. If the organic matter on land is not recycled efficiently, the organic carbon becomes fossilized and the concentration of carbon dioxide in the atmosphere begins to decline, resulting in cooling of the planet and the onset of glacial ages of increasing duration and severity. The activity of animals complements the microbial activity recycling the carbon in the cellulose of vascular plants. This operation is hindered by the devious invention of these plants: the biosynthesis of lignin, which is a cross linked polymer that, unlike cellulose, is extremely difficult to consume: the energy that is required to break this polymer nearly matches the energy generated by the digestion of fragments.

Biblical scholars rake their brains trying to understand the symbolism of the tree in the story of the Fall. There is little mystery here; they should’ve consulted a biochemist. The tree is a satanic invention through and through: magnificent, beautiful, and devastatingly deadly in its selfishness. All it cares about is not to be eaten, and so nearly 40-60% of its trunk consists of the lignin. Only a few specialized bacteria and fungi are capable of making their living out of breaking the lignin apart, and this partially degraded lignin is the main component of our soil and the precursor of fossil fuels. These lignin-breaking organisms dwell at the edge of starvation, and it is amazing that they succeeded in containment of the threat posed by the vascular plants over geological time. They are the unsung heroes of Life, the ones that make it possible for the rest of us. Sinking of the lignin by sediments coupled with the reduced volcanism of our aging planet (which results in lower emission of greenhouse gases) are the chief reasons for systematic reduction of CO2 level in the atmosphere which has been occurring over the last 100 Myr, and it is a grave danger to eukaryotic Life. The more animals graze on vegetation and digest dead wood, the better. The phototrophs have no vested interest in the existence of those who eat them, and they are capable of great devilry attempting to eliminate us. A planet with exclusively marine animal life and lush forests would be doomed for speedy glaciation.

The hyperactivity of phototrophs already resulted in several snowball glaciations before the animals had evolved, and the vascular plants are well on the path of inducing yet another global catastrophe of similar proportions. From this standpoint, the most useful of the land animals are worms and insects. The latter, however, went over to the dark side by becoming pollinators of flowering plants. It is debatable whether this defection is consequential, because the biomass of land plants did not increase significantly since the Eocene. The main innovation of the flowering plants, in terms of C sinking, is the evolution of grasslands, and insects do not pollinate grasses. Their sin, great as it is, may not be critical for the ongoing removal of carbon from the atmosphere. Said that, an animal cannot go any lower than assisting land plants in their battle for supremacy. From this perspective, our cardinal virtue as land animals is burning fossil fuels, cutting woods and expanding grasslands, thereby restoring at least a fraction of the sunk C back into the atmosphere. This is too little and too late to combat the long-term trend, but every little bit counts. We already sabotaged a minor glacial age about 8 kya, and we can and should do more. The planet has no other means of restoring healthy atmosphere than evolving the animal capable of recycling fossilized carbon. This animal is us, so we have to oblige.

There are other reasons for the desirability of land animals. After the evolution of rooted plants and the formation of soil, the rate of continental erosion markedly decreased, which resulted in the decline of mineral fertilization of the seas and the concomitant decrease in their productivity. The predominant form of marine animal life is zooplankton right at the base of the food chain. This zooplankton feeds on the phytoplankton that critically depends on N, P, Fe, and other scarce elements in sea water. Before the evolution of rooted land plants, the delivery of these minerals from the land to the ocean was more efficient, sustaining higher productivity. Declining fertilization of the ocean is yet another reason for seeking land habitats. The mere existence of land plants induces imbalances in the global ecosystem that require evolution of land animals as corrective action for the benefit of the entire animal kingdom. The alternative to the transition to land is rapid collapse of marine animal Life. The plants can care less about that.

Another reason is the one that is most frequently given in textbooks: that evolution of vascular plants created new habitats bound to be filled by animals. This is not a very good argument. There is some truth in it, of course: great evolvability of animals was conducive to the appearance of a life form capable of the transition to land and filling these empty niches. The land was colonized several times, by the ancestors of earthworms, insects, spiders, and tetrapods; each wave of colonization created the new habitat that expanded possibilities for predation, assisting the next wave. To some degree, only arthropods made this transition for good; their respiratory adaptations are such that the return to the high sea is forever closed to them; that is not the case with such quintessentially land animals as reptiles and mammals. The arthropods wholly invested into life on land and their devotion was rewarded by unprecedented diversity.

Still, the transition to land was a miracle of miracles. The animals are singularly unsuited for the existence on land. It was not obvious at the outset that it will be animals rather than another branch of Life that will become the grazers and the recyclers of land plants. Personally, I would choose the fungi and the slime molds, but I was not in charge. The great defect of animals is lack of hard material in their cell walls, as it is not required for marine life. The fungi and the plants do have such hard materials: the chitin and the cellulose, respectively. Both of these were acquired from the prokaryotes that used such polymers from the time immemorial. These materials are elegant chemical solutions to the problem of biosynthesis of rigid polymers that have low N content. Using proteins (e.g. collagen and keratin) is both prohibitively expensive and inadvisable, as their structural properties are inferior. To succeed on land, animals needed to adapt either these materials or a new way for strengthening of the body. That is because land animals continue to live in the sea: despite a few minor adaptations we still have the biochemistry of marine animals. The animal path to land colonization was to expand marine way of life onto the dry land. This is very different from the path taken by land plants that have unique cellular adaptations to their landed existence. The plants are not “algae that live on land,” but we are “fish that live on land.” These are two completely different approaches to the same problem, and it is remarkable that both are found on this planet.

The success of the arthropods was preconditioned on their acquisition of chitin, which occurred in the sea. We do not know how was it acquired, but it was perhaps from a bacterial rather than fungal symbiont. Interestingly, there are also animals that make cellulose; these animals are none others than our closest invertebrate relatives, the Urochordata. Their cellulose is clearly from a bacterial symbiont. I do not see any great advantage of chitin over cellulose, so I am hard-pressed to explain the great abundance of chitinous animals and almost complete lack of cellulose-based animals. Either way, these cellulose-sporting urochordates lived mainly sedentary lives, so it makes sense that they did not make it onto land, or may be it is. Indeed, their young freely swim before attaching themselves to a suitable surface and dissolving their notochord; it is believed that the chordates (us) originated as paedomorphic forms of these ancient Urochordates that gave up on the sedentary part of their life cycle. These infantile chordates had become the great ancestors of the animals that were last to transition onto land: us, the tetrapods. Unlike the arthropods that made it onto dry land by evolving rigid containers (chitinous exoskeletons) for hiding their marine selves, we took entirely different approach, by evolving calciferous endoskeletons. The calcification is as ancient microbial trait as the biosynthesis of cellulose and chitin; there is nothing remarkable there. The animals developed this type of biomineralization very soon in their evolution, possibly through their algal or cyanobacterial symbionts; in fact the calcification might have contributed to their explosive radiation in the Cambrian. However, that was the exoskeleton, which makes sense as a simple defensive measure. The evolution of bony endoskeleton in freshwater fish pursued other means, which remain unknown. The spikes of the calcium carbonate might have developed as the means of calcium regulation in mineral poor environments, or as the means of making these fish less palatable to their predators. In any case, the bone initially had no structural function and it is amazing that it developed at all; nothing heralded that this adaptation would be useful on land. Again, this is quite different from the possessors of chitinous exoskeletons which are as useful in the ocean (for protection) as on land (for containing hypersea environment). The transition of creeping arthropods onto land couldv’e been expected. The transition of the vertebrates would be unexpected by any disinterested observer of ancient animal life. Even today, the contribution of the vertebrates to land ecology is barely noticeable: unlike the arthropods, the chosen land colonizers, they do not play any globally useful function. There was and there remains no “need” or necessity in the transition of our four legged ancestors onto land.

We make great deal out of ourselves and the evolution of our lineage, which is evidenced by the interest in dinosaurs, Pleistocene mammals, Lucy the hominid and other marginalia. In any museum of natural history, the least visited sections are on invertebrates and plants, although theirs is the world. These prehistoric beasts had eventful and dramatic lives, but neither their diversity nor their impact nearly approached a fraction of those of the roaches, beetles, ants, and bees. One has to be a tetrapod to notice their existence at all. Since this is a bitter pill to swallow, we are consoled that we are more “complex” than, say, the insects. That is anthropocentric nonsense. The insects are as complex as required for their life, and their interactions, social organization, the variety of their life cycles, and the sheer number of their predative and defensive strategies easily match and exceed the complexity of “higher” animals. Incidentally, most of our “complexity” is adaptations acquired to overcome our structural deficiencies; better designed land animals do not need it. The truth is that the vertebrates could’ve never existed, and no one would take notice. That we find ourselves on land and at the top of the food chain is a sequence of freak events that have murky origins and no apparent goal.

Or does it? The answer depends on whether one regards the evolution as an aimless process or the means of getting somewhere. If the eukaryotic evolution is striving towards a new Gaya, our finding ourselves on land is neither random nor unexpected. Other land animals do not have the lung that allows us to reach almost any size without paying penalty in metabolic activity. The lung is not only useful on land, it allows land animals to go back to sea, escaping periodic extinctions and maintaining the continuity of lineages. The arthropods cannot go back anymore; their recipe for avoiding mass extinctions on land is through their diversity. Despite all that diversity, there is a fundamental limitation on their size: they have to be small, as their intake of air is diffusive. The only time when they were able to grow large was a brief period of time when the concentration of oxygen in the air increased to 30-40 vol%. Such a situation cannot be maintained in a long run, because high oxygen concentration causes widespread fires and increases the oxidative stress on all Life, so the Gaya works against it. Short of this short-lived bonanza, the arthropods never managed to become large. They gave up and chose miniaturization and predative inventiveness over their size. Not us: we, the tetrapods, never had this problem. Our evolution was slow and, I’d say, pretty low on innovation, with the exclusion of the controlled flight and periodic transitions back to sea. The repeated feature of tetrapod life in many lineages was the constant increase in body size, which is made possible by the lung. This increase is mainly due to the predator-prey interaction: the prey increases their size to evade their predators; the predators increase their size to match their prey. The dinosaurs and marine reptiles of the Jurassic illustrate how far this competition might go if there is no limitation on size. In other words, if one wants a large animal, then the arthropods are no-no, whereas the tetrapods is exactly what is needed. Never mind that large animals are ecologically unimportant; if one’s goal is to have large animals on land, the ecology exists for supporting such animals rather than the other way round.

But why would such land animals be the intermediate “goal” of evolution? The large body size creates the possibility – and it is only a possibility - for the development of greater intelligence, through the increased size of the brain. It is only one of such possibilities, but it cannot be overlooked. For small animals, like insects, the only rout to greater intelligence is through the increase in their interactivity and social organization; in some ways, this rout would accord more with the final goal of the evolution, which is the destruction of eukaryotic individuality. The social insects may eventually succeed with their approach, especially if our rout to integration which is based on the increase in the individual intelligence will dead end, but for now we have the edge. The formidable obstacle for the arthropods is that communal thought, unlike communal digestion, is harder to achieve biologically, although I see no principal impossibility there. One should not discount marine animals, too, as they too can be any size. However, large marine animals are particularly susceptible to anoxic stress and changing ocean chemistry. Excepting sharks, it is hard to find large cranial animals that made it through the last three mass extinctions. As pointed out, lunged animals are better secured against such global upheavals, and the evolution of intelligence is slow and takes time.

These considerations suggest that the speediest and the safest path towards the evolution of individual intelligence goes through the evolution of large animals on land. It does not matter which adaptations the latter acquire to sustain their body size or what role may they play in the biosphere. If the goal is acquiring a certain level of intelligence in an individual, these animals are the way to go. The large size does not automatically mean better brain; the brain the size of a grapefruit can be attached to the body the size of a hill. But the inherent possibility for a larger and more complex brain exists. The “man” thus becomes a possibility; perhaps even inevitability. The exact path towards the “man” is unimportant; all that matters is what it will be capable of. This new quality is required for the transformation the evolution seeks. We are coming to the last day of Creation.

Why are we land animals?

The making of a human animal

...Then God said, Let us make man in our image, after our likeness; and let them have dominion over the fish of the sea, and over the birds of the air, and over the cattle, and over all the earth, and over every creeping thing that creeps upon the earth. Gen. 1:26

Creating a man is not a straightforward task, and the last leg of the transformation of stardust into a human being was as convoluted as its first. The group of animals from which we descend, the mammals, have been around for quite a while; our beginning is as ancient as that of the dinosaurs. We are older than the fish in the oceans, the birds in the sky, the apple trees in the garden, and the bees pollinating these trees. The first mammal-like reptiles, a small twig of the vast reptile tree, branched off the main group around 230-260 Mya, in a world as different from ours as can be imagined. Nothing about these animals suggested that they wouldn’t disappear as soon as they evolved. Our chief defect was that (for poorly understood reasons) we became warm blooded in a hot, humid world. This adaptation is seen as blessing, but it makes preciously little sense for mammals. It requires constant intake of food, it shortens our lives, it makes us the perfect target for infrared vision, it makes us easier to smell, it sets constraints on the development of our internal organs, which provide the heat, it makes us vulnerable to hypothermia, it requires fat and hair for thermoregulation, it increases our parasitic load, it requires the development of hyperactive immune system to combat the parasites. The list is very long indeed. Unlike the birds that need to fly, we have no real need in increasing our aerobic capacity. Many small mammals live underground where the temperature is more-or-less constant all year. The mammals appeared during one of the warmest periods in Earth’s history, when retaining of the heat was not required. One theory is that high body temperature was needed to cope with the stress of raising young that required very active foraging. That may be true, but who says that the young have to be taken care of. Having fewer young that need to be fed and protected does not seem to be superior to having plenty of young that are left to their own fate. Furthermore, it is not clear why hot bloodedness should not be restricted to the breeding period (as happens in some animals) or just a few organs (as happens in other animals). No matter how one looks at it, this defining trait of the mammals makes no biological sense.

Little wonder that this joke of an animal was a failure. Constant foraging for no other reason that warming the environment is not conducive to evolutionary success. The proto-mammals have been drifting downwards into marginal habitats. Shrews, moles, and small insectivores we were. That served us very badly. Our short lifespan became even shorter, as the pressure of predation limited the life span from above, so the main defense became early breeding; the fate of the animal after breeding became unimportant. The vision declined and became black and white, as nothing else was needed for underground and nocturnal existence. The visual cortex also declined and the development of the brain, our only edge as hot blooded animals over the reptiles, also stalled. The existence under the iron heel of the dinosaurs continued for tens of millions years. The future looked bleak. However, even in these darkest days of the mammals, there was hope. About 90 Mya, the mammals found a new place to hide: the trees. These were the ancestors of the primates. Living in a new habitat began a positive trend in the mammalian evolution. The need for improved vision and better coordination placed us back on the road to the development of better brains. It actually helped that we lost so much, because the brain took upon itself the tasks that in other animals are carried out by specialized organs. For example, our color vision, which is still greatly inferior to that of other animals, is based on our ability to distinguish between the inputs of two photoreceptors with largely overlapping absorption spectra. Our smarts were partly developed to compensate for the inferiority of our kind traceable to the millions of years of woe and subjugation. The first true mammals are found around 70 Mya; our monotreme relatives - arond 125 Mya.

Then a miracle happened. The dinosaurs were gone, almost in an instant. We have no clue how it happened. The popular vision of an asteroid delivering the mammals from their reptilian oppressors is correct in fact (there was an impact) but not in substance. The ensuing calamity wiped out the dinosaurs, in all niches of life, everywhere, all of them, regardless of their size and the position in the food chain, and left frogs, lizards, crocodiles, mammals, birds and the like. The reason was not heavenly, it was earthly. The dinosaurs missed the critical adaptation that allowed these other animals to survive the ordeal. We do not know what that adaptation was, and we have little hope of finding out. The point is that this adaptation was not required for over 165 Myr of their unquestioned rule, and when they needed it most, it turned out that neither they nor their marine relatives have it. It could be resistivity to a certain type of a virus, it could be anything; I do not want to guess. The point is that even closely related beasts (such as the mammals; other, more primitive reptiles; the birds, etc.) made it through - with great losses, of course, - but the land was swiftly emptied of its top predator. The survivors, including the mammals, were given their chance to thrive in this new world.

They blew that chance, too. The overlordship of the dinosaurs passed to flightless predatory birds. The typical scene of that brutal era was a large hook nosed bird chasing a horse the size of a lapdog. At first look, nothing changed – but everything had changed. The adaptations of the mammals, which were previously useless, began to pay off. The end of the dinosaurs was more than just their own end. It was the end of the era. The flowering plants reached the tree size and started to replace conifers. There were fruit and berries to eat, not just seeds and leaves. There was an explosion of insect diversity connected with the radiation of angiosperms. These insects were slimy yet delicious. Foraging for food became easier. The climate began to change; it became colder: hot blood began to be an advantage; it was also easier to maintain. Another advantage was that the predators were also hot blooded, and so they suffered from the same problems and limitations as their prey. The primates thrived: living in the fruit-bearing trees was good: the pressure of the predation was low, there was plenty to eat, and there were endless forests to occupy. It was summer time, and the living was easy.

On land, however, it was murder. Then another miraculous delivery occurred. The climate became cooler and more arid, and the forests began to decline. The flowering plants ceased this opportunity, became grasses, and covered the planes. A new habitat, the grassland, was created, and grazing on grass became the opportunity the mammals have waited for so long. In the open, they grew bigger and bigger. The birds of prey, whose size is limited by their vestigal flight adaptations, were not able to cope and they lost their top position in the food chain (except in South America). The mammals began hunting mammals. The age of the mammal arrived, and 50 Mya the mammals rapidly diversified.

The primates were not the beneficiary of this brave new age, because the grasslands were not their habitat. Then the disaster struck. The new enemy was faultless. It was able to move silently. It saw the primates in the dark. It had better vision and it had better sense of smell. It was able to digest everything including their bones. It targeted their young. It was cold blooded. It had poison. It was perfection. The Fruit lured the primates into their arboreal Eden. The Snake drove them out from of it. The first response was to evolve a smarter primate capable of better individual and collective defense. Full color vision and rapid detection of movement developed, more complex social structure appeared, and the switchover from nocturnal to daytime living followed; all these developments required better brains. The main problem for the arboreal mammals was that they were unable to have passive defenses possessed by their land relatives, as they had to be maneuverable. Their only defense was in getting smarter, and so the primate became an ape. That worked for a while, but the deforestation continued, and another strategy was called for. There was no safety anywhere anymore, especially on the expanding plains, whereas the groups of trees became too isolated to provide more than temporary relief. The apes needed to get from one woody patch to another by walking on the grassland, where they were exposed to mammalian predators that wasted no time to evolve into efficient killing machines. The apes had to run and develop collective defense in which individuals are sacrificed for providing the opportunity for the group to move around. Bipedalism and closely knit communities addressed these concerns. The apes grew larger and stronger, as do other animals on the plains to reduce the predation.
The larger is a hot blooded animal, the more food it needs. The food on the plains was scarce, as the primates got there so rapidly that they failed to develop complex stomachs needed for digestion of grass. Their other failure was inability to compete with the predators. The only way of complementing their meager diet was through scavenging, and the ape became a scavenger. However, the apes are not natural scavengers, so they became dependent on the skill they learned in the forest, but used sparingly: tool making. Another defect from their previous life was poor digestion of starchy foods that were found on the plains, due to their poor teeth and short gut. Making an ape into a savannah animal seemed hopeless from the start; it would require prohibitively long period of time. As the predators do not wait, it was another dead end.

Except it was not. The new adaptation of these bipedal apes was unprecedented. Not once in the previous 3.5 Gya there was a life form that used fire. There are animals using poison, there are animals using acid, there are animals using steam; there are no animals using fire. The hominids did. How they began using fire is a mystery, but as soon as they did, it solved all of their immediate problems. It solved the problem of the defense. It solved the problem of the digestion. It solved the problem of efficient scavenging, as it allowed storing and cooking food. The fire needed to be protected and fueled; the hominid rose to the challenge. Its nutrition improved drastically, and that caused another wave of useful adaptations. Bigger size became possible, bigger brain became possible, complex social structure became possible. The human animal was almost complete.

What completed it? The popular answer is that it was language. The theory goes that we had the dormant ability for speech for hundreds of thousands of years, but it was not used. When it began to be used around 150 kya, it spread across the dispersed human settlements like wild fire and the transformation from the hominids to the humans occurred in a few generations. Like other anthropological theories, this one is impossible to prove or disprove. Chimps can be taught to use sign language almost as well as little kids, and I do not think that the hominids suffered from lack of communication. There was some kind of language, which probably involved vocalization, well before human language, and perhaps it was fully suitable for expressing all thoughts needed to be expressed by our ancestors.

Then they started to have different thoughts, very strange thoughts indeed. The thoughts of cold and hunger, of hunting the mammoth and making the stone hammers were easy to communicate. These new thoughts were not. One of their thoughts in particular resisted all means of nonverbal communication.

The human animal became Man.

What Man is for?

...So God created man in his own image, in the image of God he created him; male and female he created them. And God blessed them, and God said to them, Be fruitful and multiply, and fill the earth and subdue it; and have dominion over the fish of the sea and over the birds of the air and over every living thing that moves upon the earth. And God said, Behold, I have given you every plant yielding seed which is upon the face of all the earth, and every tree with seed in its fruit; you shall have them for food. And to every beast of the earth, and to every bird of the air, and to everything that creeps on the earth, everything that has the breath of life, I have given every green plant for food. And it was so. Gen. 1:27-30

Why are we here? What is our future? Why do we have “moral compass” telling us what is good and what is evil? In what way are we different from animals? Who are we?

All of our science, philosophy, art, and religion are seeking answers to these questions, and our sages tell us that seeking these answers is the meaning of our lives. Strangely, the science that tells us so much about stellar evolution, subatomic particles, biophysics of the cell and other esoteric matters falters increasingly the closer we get to ourselves. The evolution and the origin of humans, understanding of intelligence, consciousness, language, morals – and all the rest - stubbornly remain the least developed areas of natural sciences. This is very surprising because the subject of these studies is well known to us; in fact it is more familiar to us than anything else that we know: ourselves. It could be, of course, that our knowledge of other things is as illusory: it is easier to notice the failure of the method on a more familiar object than on a less familiar. The last thing I’d like to hear about the evolution of humans is a lecture on the changes of cranial cavities and the shapes of stone scrapers, just like the last thing I want to know about astrophysics is a lecture on how to spot zodiacal constellations. Not that these matters are unimportant; rather, such an approach is so far off the mark that it is hard to treat this kind of science seriously. Such studies are being done when nobody has a clue how to approach the problem. That is my general impression of the studies of human qualities: barely scientific methods, largely pointless studies, fantastic yarns packaged as theories, and no real progress. It does not seem to work, despite a good deal of effort. Then, how are we supposed to know ourselves and have meaningful lives? It all looks rather hopeless. It is so much easier to know things other than ourselves, like neutrino oscillations and aerodynamics… So we study those other things. That works, but it does not answer the questions posed above.

One of the problems is that we are alone. There is no broader perspective, no one to compare ourselves to; it is not clear what is important, what is superfluous, and what is accidental. We cannot have cold, objective look at ourselves, and there is nobody around to supply it. It would be preposterous to claim that I can look in such a way; rather I suggest the perspective that takes something that is very familiar and places it into a larger picture. It is not the humanity that interests me; it is the direction of biological evolution and the goal of the creation in general. Without a speculative guess about this direction and this goal, answering the title question is not just hard, but impossible.

As discussed before, I believe that the evolution is aiming at the creation of eukaryotic Gaya, the new form of Life that is terrestrial in origin, but has the character of prokaryotic kingdom: the complete integration, lack of individuality, immortality, and the total control of the habitat. The evolution stops there, because there is nothing else to achieve. The future of this new Gaya would be to pollinate other planets. Nothing else remains to do on Earth, and that’s for the best, because in 0.5-1 Gyr, our planet will enter the period of terminal instability before it will be annihilated by heavenly fire: the expanding Sun reaching its red giant phase. The future of Life on earth is Armageddon. The survival is through cosmic expansion, but the current eukaryotic Life is unsuitable for terraforming operation required for such an expansion, because this operation cannot be carried out by atomized individuals preoccupied with killing and eating each other. Either the character of the eukaryotic Life will change, or it will disappear without trace. There is another consideration. Life on Earth will perish regardless of this expansion. The cosmic expansion is not for the sake of the terrestrial Life; the latter will be gone, never to be replicated again, with its home planet. The seeds of Life sown on other planets will begin their individual paths, which will be uniquely crafted to their new habitats, and in time bring forth their own unique forms of Life, derivative of ours, but theirs alone. The cosmic phase is not for the sake of our Life on our planet, it is for the sake of Life in general, Life as cosmic phenomenon. Such an act is very familiar to us as individuals; that is what being fruitful and multiply is about: we die and our children carry out their own lives, with some of our traits present in them. It has to be done on the global scale, for the entire terrestrial Life. It cannot be presently done; we are not at the budding stage, when it can be done. Biological evolution is the maturation of eukaryotic Life required for its survival through budding. This maturation presumes the redemptive correction: Life cannot spread when it remains the battlefield of individuals.
The first step towards this correction was the evolution of a multicellular organism. The second step will repeat with the organism what has been achieved at the cellular level, but differently. Many of the ways have been tried, but the goal remained elusive. The important thing is that it is being tried on a very large scale, so it will succeed one way or the other. However, to succeed fully the new entity has to evolve a new concept of individuality, and that requires more abstraction than a typical animal is capable of, so the boost of intellect is required. One of the possible routs to the unification is through evolving greater individual intellect in large land animals, and here we come into play. The sixth day of creation is achieving the critical level of intellect in one animal, so this animal can develop a thought of superindividual existence and then strive towards its implementation.
We are such animals and we did develop this thought; it is precisely the thought on which all of our religions rest and our history begins when and only when this thought was developed, quite possibly accidentally and certainly not right away. Increased brain, acquisition of language, tool making, agriculture, civilization, science, and so on were important developments but all of these developments count less than this one thought. In the language of the Bible this thought is called knowing God. This knowledge is what gives us transformative power and where our promise resides. The redemption of the terrestrial Life may occur through us; more correctly, it may occur through what will begin with us. However, it may occur differently, by other means -- if our promise will not materialize. As humans, we have no stake in this redemption, because the realization of our promise means the end of humanity as we know it; our species has no future. The question is exclusively about what will come out of us, it is not about us. We can do a great deal, but we cannot do it for ourselves.

Our predicament is that this transformative thought contradicts everything that the previous 1 Gyr of evolution were about, which is strengthening of the self and the development of the concept of individuality suitable for such fortified selves. This baggage is the major hindrance for the unification and it may well be the cause for the failure of this particular approach. In an intellectual animal, the satanic mark is present as a thought of the self, and it comes with the built-in perspective of classifying everything into “good” and “evil.” Good is what strengthens the individual, and evil is what weakens it, from the standpoint of the individual. This perspective is false, but it became embedded in us; we cannot think of anything without classifying the subjects this way, even if unconsciously. Perhaps early on, this classification worked only on the subconscious level, but at some point it became conscious; we acquired the knowledge of good and evil, and that moment was our Fall. This knowledge is the rebellion of individuality that found the new arena for its derangements: our conscious thought. We were not created for this sorry situation; we were not “supposed” to acquire this knowledge, because it is false and useless for our mission. But we did, and there is no way back. The human history began.

The battle of the two concepts of individuality began right away, because these two are fundamentally incompatible. One leads forward, but requires the aspirations of inhumanity and the refusal of the self, another leads back to animality and the submission to the self. Any movement, however small, towards the loss of the self cannot be “good,” by definition; our animal nature revolts at the very thought of it. On the other hand, the other program commands us to do just that. This schizophrenic situation had to be resolved, and it resolved itself in morality. We are told that the morality can be summed up as the golden rule. It can be summed up shorter. Morality is unselfishness; in all moral systems, the unselfishness is the greatest “good.” All of our ethical theories, moral teachings, and holy books are trying to explain why that is so, because such explanations are badly needed. The problem is that the unselfishness is not “good.” For lack of the internal ability, we use the good-evil category for the one thing it cannot classify. Perversely, the complete opposite of “good” has to be regarded as the highest good. All of this shows that the humans are a transitory form, like protoeukaryotic chimera; it’s the contradiction embodied. The pain could have been avoided would we not acquire the knowledge of good and evil. This knowledge is the main source of evil in our lives.

Morality aims to make sense of this strange situation, by translating the untranslatable into the language of “good” and “evil.” It is divinely commanded, because it rationalizes the purpose of our existence, but it is human invention, and that is why there is a variety of moral codes and laws. All these codes and laws do not prevent us from doing selfish things, but at least we know we sin. No amount of social change is going to make the slightest difference in this respect.

So, how are we doing and what awaits us? Many would disagree, but we are doing fine, given the gravity of our situation. There is still promise resting in us. We may live our destiny; no great errors have been made. I cannot say how it will be done and what will be the first step; perhaps the formation of the human society was that step already. We are getting smarter. We are trying to learn things that may help, exactly the things that are going to help. What some of us are desperately trying to learn about ourselves is futile and not going to help. The task of understanding humans cannot be carried out by humans. They may try, it will be all the same. Nor does it matter. The idea that gives us the power and the aspiration to achieve the impossible is still with us, it is still growing and developing. Our society is becoming more complex, and it is gaining control over the planet, we already have global consequence. We even peeked outside and visited other planets of our system! That was an enormous path to travel in 100 kyr. There are reasons for cautious optimism.

The future of Life may go through us -- or it may not. It will happen with or without our help; I wish we’d help. The timing is good. We are roughly in the middle of good times; there is another 500 Myr to go. There is plenty of time ahead, and the previous 500 Myr were used very well; biological evolution was a marvel. We will have wonderful future; not us, of course, but what we will create. I wish we would see this redeemed, purified Life at its greatest moment, when its seeds depart to their new celestial homes. But we cannot and we wouldn’t.

Epilogue.

...And God saw everything that he had made, and behold, it was very good. Gen. 1:31

The road leading from Big Bang to the person writing this sentence has been long and windy. Its terrestrial phase took 4.5 Gyr, its eukaryotic phase took 1.6-2 Gyr, its animal phase took 540 Myr, and its primate phase took 90 Myr. These are mind boggling figures. People do not dream of creating over such stretches of time. Can it be done faster? Should it be done faster? Does it make sense to rely on a random process for achieving a deterministic goal?

The answer to the last question is obvious: it makes perfect sense and we do it every day. Consider boiling water. What may appear chaotic to bubbles and molecules is a mundane operation whose general outline is entirely predictable. We do not ensure that each bubble is perfectly round and the temperature is uniform, although we can. We do not trace the fate of each individual atom inside the pot, although in principle we can. This type of knowledge and this type of control are possible, but these are not needed to put water to boil. All that is need is general knowledge of the most probable outcome of transferring heat to a body of water. Biological evolution is the same. The chaotic nature of the process makes detailed predictions as hard and time consuming as the process itself, but the general direction and the outcome are probabilistically predictable. The only thing that matters is the final outcome. Humans are not this outcome; we are one of the dancing bubbles. The evolution does not lead specifically to us and it is not aiming at us, but it is impossible to have boiling water without bubbles.

A creature that has man’s abilities can be made in infinite number of ways that may take longer or shorter periods of time. If time is not of essence, and our perception of time is framed by the brevity of our lives, any one of these ways would do. However, man was not just made, man was created. Creation presumes unexpected result. When the result is totally predictable, such an act would not be called creative. One tries one’s best and then declares the result good – or needing improvement. We have the ability to create because we cannot predict the outcome of our actions. For someone having such ability, the creation poses a problem whose only resolution is either willingly refusing to predict, which may or may not be possible, or making the prediction as hard as creation itself. In the latter situation, the best way of gaining knowledge is running the show and observing the result. Other ways of knowing may exist, but such ways are in no way preferable to running the show. Omniscience presumes the ability to know everything. It does not point to the way in which such knowledge can be obtained in the most efficient way; it does not even specify the character of such knowledge. Making things through creation implies fundamental randomness and poor predictability of intermediate results. This does not exclude determinism, but the path towards the goal can only be probabilistic and the end point can only be defined generally, like boiling water. The details and the specific path do not matter. Alas, it is a different story to the creatures finding themselves in the midst of it. It would be nice if the Universe were designed specifically for us. A quick glance around suggests the opposite. We are not the end point of the creation and we are not put together with infinite care. We are only part of a random process; our involvement in this process is transitory. That does not mean that our role is negligible.

There are excellent reasons to expect that biological creation would be evolutionary, because the evolution does not exist in vacuum. There is geological evolution, evolution of the solar system, galactic evolution - all occurring simultaneously and all relying on organized randomness. This is such an inherent property of creation that having purely deterministic process in some corner of the Universe is all but impossible. This corner has to be totally protected from the interference from the rest of the creation. The robust Life has to be immune to random interferences. Only a system that is itself built upon randomness can guarantee that Life will have chance for survival, despite all these tribulations. Once the world is being made through creation, there is little freedom left to achieve stability by other means than creation.

A man can be made in an instant. No miracle is required for that. Nothing in the laws of nature precludes the possibility of appearance of men, cows, earth, or the entire visible Universe as random combination of particles. The probability would be astronomically small, but the Universe is vast, possibly infinite, and such improbabilities are probable. If this statistical anomaly were the goal, if specifically men and our current habitat were the goal, there would not be any need to create. So the goal must be such that its realization is not the statistical nonety but a high degree of certainty. What is loftily called “intelligent beings observing the Universe” by the proponents of the anthropic principle cannot be such a goal. These proponents shy away from giving universal definitions of intelligence, beings, Life, etc. This refusal nullifies the argument. What is the proof that different laws of nature would not produce intelligent observers? Are photons, atoms, boulders and stars intelligent observers? The claim does not go further than concluding that different laws of nature would not produce the observers of exactly our type. That is correct, but what is so important about us? Forget different laws of nature. The very fact that we have eyes is accidental. Would we live on a planet with denser, hazy atmosphere, vision would be useless. The mammals have the poorest vision among higher animals; we are lucky to have any vision at all. And that’s just the beginning. Would our solar system be immersed in a dense cloud, we would not see distant stars and galaxies, etc. Intelligent observers of the Universe are we indeed.

The path to “intelligent observers” is too checkered to take their intelligence, their ability to observe, and their interest in observing the Universe for granted. One may say that the Universe was designed to make cave salamanders, so that they can smell their cave. One may say that the cave is smelly because cave salamanders cannot be found in the caves that do not smell. Both of these viewpoints ignore the fact that there is more to the Universe than smelly caves and salamanders. I am afraid that the Universe does not exist for intelligent observers; least of all it exists for the self-appointed observer called H. sapience. Intelligent observers may be the means to a goal; this goal should be achievable without them.

What is this goal? I believe that this goal is eternal Life. It does not merit definition because it is more basic and permanent than the Universe itself. The fundamental problem with Life in our Universe is that it exists in the world that cannot support it forever. I do not mean the end of the Earth. The problem is bigger; it remains even if there is cosmic abundance of Life. The problem is the accelerated expansion of the Universe that dilutes the sources of energy available at any given point. In the distant future, the galaxies that make the local group will merge and the resulting mega-galaxy will be increasingly isolated from other galaxies and intergalactic reservoirs of hydrogen. Eventually, this island galaxy will run out of fuel; there will be no new stars formed, no new planets, only dead, cold remnants: black dwarfs, black holes, etc. Technically, this island world may exist in perpetuity but from the standpoint of Life it is dead. Eternal Life is not possible in our universe. The survival of Life depends on the creation of a new universe. It cannot be a virtual world, because there will be increasingly diminishing resources required to run this virtual reality on top of the old one. It has to be a new reality, a new universe. The sad fact is that the inhabitants of the old reality might be able to create the new one but they cannot inhabit it. Their future is death or something worse than death: eternal dying in a cold, dying world. The creation of the new world is the ultimate act of selflessness: it ensures the continuity of Life through the new beginning and it gives the new world the form that is conducive to Life that creates it, but the creator of the new world has no stake in it. The creator can only create it and love it, it cannot escape into it. As we are created in the likeness of this creator, we know this feeling all too well: our lot is also to die. We cannot escape into our children and things that we create. The path to eternity lies through the denial of the self.

The creation that I placed into the future can be placed into the past, and that is why Life is eternal. As a cosmic phenomenon, Life is being fruitful and multiplies through the creation of inhabitable universes. These universes may come in radically different fashions, or there may be preferred designs. The choice is that of the creator. Ours is the best possible world for the Lives of our type. Life has no other goal than survival and proliferation; we know this very well. As soon as this feature is extrapolated far into the future, it implies creation. And so the goal of Life is the creation of new universes inhabitable by Life, starting from scratch. Whether this goal is achievable through the creation of “intelligent observers” or seraphim is superfluous. There is, however, one thing that matters: only unselfish Life can be expected to multiply by creation. Selfish Life will do everything possible to survive itself in its universe instead of giving the new beginning. Perhaps the Hell is the world inhabited by this selfish Life knowingly and in vain striving for impossible but unable to make the sacrifice. I do not believe that this is our future. I wish for a very different future:

That men will begin a new day of creation resulting in eukaryotic Gaya. That this new form of Life will be able to spread across the Galaxy and inhabit and transform other planets. That these Lives will be able to capitalize on the last wave of star formation during the galactic merger. That homogenization occurring during this merger will make the contact between these and other Lives possible. That out of this accretion of Life a new form of Life, the Creator, will emerge that will develop the means and the ability to create new universes. That it will succeed in starting the new Beginning and the creation will continue indefinitely. It was so, it is so, and it will be so.

In the Beginning...

Afterword

I dedicate this series to the memory of my father, Alexander Shkrob. Many of the ideas given here belong to him; I did my best to expand and explain these ideas and shape the narrative. I had to rely on recollections of conversations of 20, 30 or more years ago; no written account remains of father’s “creation stories.” I do not know whether he believed in what he told me or just amused himself by teasing me and exploiting my curiosity to teach me some science. My father was a man of extravagant, fascinating views which he usually kept to himself. Perhaps that’s for the better, because many of these views were extreme and generated hostility. I never understood this reaction, because even when I disagreed with his views, which was frequently, I found them interesting and worthy of taking seriously. It was great surprise to me when I discovered that not all of the people have forceful opinions summing up their entire personality. Unfortunately, I cannot replicate father’s presentation of his stories that was as involving as their content.

There is a popular genre of literature called science fiction. As a rule, there is no science and not much fiction in this “science fiction.” Seldom does this genre, even at its best, aspire to assist scientific imagination by supplying fiction. Darwin’s books are still unsurpassed in this respect. Father’s stories were in the same vein. His fertile imagination melted together the most uninhibited science with the most daring fiction into a form for which there is no name. The past, the future, the knowns and the unknows all went into it and blended with his own wild guesses and speculations. His stories were improvised on the spot and delivered without any system; only years later, by replaying these stories in my head, did I notice common threads and guessed what kind of worldview might’ve underpinned these stories. He never told me, and it is too late to ask. I may be wrong in my guesses.

In the end I cannot tell who was the author of this commentary to the first chapter of Genesis: the father, the son, or the spirit commanding us to recite the story of the Beginning.