Evolution of Earth
Evolution of Earth.
The journey of the Universe began some 14 billon years ago.
The Universe emerged from a hot, dense sea of matter and energy.
As the cosmos expanded and cooled, they spawned galaxies, stars, planets,
and eventually life.
Not much is known what came before the Big Bang.
We do know now that it launched a sequence of events,
that gave rise to the universal laws of physics,
and the chemical elements that makeup matter.
How the Earth came about, and life subsequently followed,
is a wondrous story of time and change.
Big Bang and Hadean Eon.
The Big Bang formed the entire Universe that we know, including the elements, forces,
stars and planets.
Hydrogen and massive dissipation of heat, dominated the initial stages of the Universe.
During the time span known as the Hadean Eon,
our solar system formed within the large cloud of gas and dust.
The Sun’s gravitational pull brought together spatial particles,
to create the Earth and other planets.
They would take a long time to reach their modern forms.
Archean Eon (4-2.5 billion years ago).
After its initial formation 4 billions years ago, the surface of the Earth was extremely hot,
and entirely liquid.
The subsequent Eon saw the planet cool down massively,
solidifying some of the liquid surface.
This gave rise to the continents and the oceans, as well as the first recorded history of rocks.
Early in this time frame, known as the Archean Eon, life appeared on Earth.
The oldest discovered fossils, consisting of tiny preserved microorganisms,
are about 3.5 billion years old.
Paleoproterozoic Era.(2.5-1.6 billion years ago).
The first Era of the Proterozoic Eon, the Paleproterozoic Era,
was the longest in the Earth’s geological history.
Tectonic plates arose and land masses shifted across the globe.
It was the beginning of the formation of Earth, we know today.
Cyanobacteria, the first organism using photosynthesis appeared during this period.
The photosynthetic activity brought about a rapid upsurge in atmospheric oxygen.
This resulted in the Great Oxidation event.
This killed off many primordial anaerobic bacterial groups.
It paved the way for multicellular life to grow and flourish.
Mesoproterozoic Era.(1.6-1 billion years ago).
The Mesoproterozoic Era is known as the ‘boring billion’ stage of the Earth’s history.
This is due to a lack of widespread geochemical activity,
and relative stability of the ocean carbon reservoirs.
This Era saw the breakup of the super continents, and formation of new continents.
The period also saw the first noted case, of sexual reproduction among organisms.
It was the probable time of the appearance of multicellular organisms, and green plants.
Neoproterozoic Era. (1billion - 542 million years ago).
The Neoproterozoic Era is one of the most profound time periods in Earth’s history.
Its bookends two major periods in the planets evolutionary timeline.
The period of proximately microbial life on one side, and the period of introduction of diverse,
multicellular organisms on the other.
During this time, Earth experienced severe glaciations, known as the cryogenian period.
This was the time of the first ice age, also known as snowball Earth.
This Era saw the formation of the ozone layer.
It was the time early multicellular life emerged.
These were hard-shelled animals such as trilobites and archaeocyathids.
Paleozoic Era. (541 million - 252 million years ago).
The Paleozoic Era is best known for ushering in an explosion of life on Earth,
with two of the most critical events in the history of animal life.
At its beginning, multicellular animals underwent a dramatic Cambrian explosion,
in aquatic diversity, and almost all living animals appeared within a few million of years.
At the other end of the Paleozoic Era, the largest mass extinction in history,
resulted in 96% of marine life, and 70% of terrestrial life dying out.
Halfway between these events, animals, fungi, and plants colonised the land,
and the insects took to the air.
Mesozoic Era. (252 million - 66 million years ago).
The Mesozoic era was the age of reptiles.
Dinosaur’s, crocodiles and pterosaurs ruled the land.
This era can be divided into three periods of time.
- Triassic (252 to 201 million years ago ).
- Jurassic (202 to 145 million years ago).
- Cretaceous (145 to 66 million years ago).
One of the earliest dinosaur, was a two-legged, 3 feet long, dinosaur called Eoraptor .
Scientists believe that the Eoraptor, and a few other dinosaurs,
evolved into the many species of well known dinosaurs, that would dominate the planet,
during the Jurassic period.
They would last well into the Cretaceous period, when the asteroid chicxulub impactor,
crashed into the Earth.
This ended the age of reptiles.
Cenozoic Era. (66 million to present day).
After the end of the dinosaurs, this era saw massive adaptions,
by natural flora and fauna to survive.
The plants and animals that formed during this era look most like those on Earth today.
The earliest form of modern mammals, amphibians, birds,
and reptiles can be traced to the Cenozoic era.
Human history is entirely contained during this period,
as apes developed through evolutionary pressure,
and gave rise to the present day human being or Homo sapiens.
Compared to the evolutionary timeline of the world,
human history has risen quite rapidly and dramatically.
Going from the first stone tools, and the age of kings,
to concrete jungles with modern technology may seem like a long journey,
but compared to everything that came before it, is but a brief blink of an eye.