GENESIS and the TWILIGHT ZONE

Partial Recovery of Inconvenient Truth 

 

Part III - Anatomy of Human Evolution

Introduction

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Our Primate Origin

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To understand human evolution one must understand where humans fit in relation to other forms of life. Modern humans belong to the group of mammals known as Primates. This is the scientific category describing such diverse creatures as lemurs, lorises, tarsiers, the monkeys of the New World and Old World, and also the apes. As primates we all share many characteristics, such as overlapping fields of vision caused by forward looking eyes (this allows for greater 3D vision), fine ability to grasp and handle objects in our hands, and enlarged brains relative to body size. The evolution of the Primates started in the early part of the Eocene epoch (about 55 million years ago).

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Chimpanzees and humans are more closely related to each other than either is to gorillas. However, it must be stressed that humans did not evolve from living chimpanzees. Rather, our species and chimpanzees are both the descendants of a common ancestor that was distinct from other African apes. This common ancestor is thought to have existed in the Pliocene between 5 and 8 million years ago, based on the estimated rates of genetic change. Both of our species have since undergone 5 to 8 million years of evolution after this split of the two lineages. Using the fossil record, scientists attempt to reconstruct the evolution from this common ancestor through the series of early human species to today's modern human species.

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So when did humans originate? The answer to that question really depends on what traits are meant by the term "human." Our understanding of the fossil record shows that distinctively human traits appeared neither recently nor all at once. Rather, they evolved piecemeal over a period of roughly 5 million years. By 4 million years ago, humans were habitually bipedal (walking on two legs) yet had brains roughly a third of the size of a modern human's (about the size of a modern ape's brain). By 2.5 million years ago the manufacture of stone tools was common. Large increases in brain size occurred even later. Complex behaviors such as adaptation to a wide range of environments and cultural diversification emerged only within the last 100,000 years.

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Human Transformation

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Human transformation is the lengthy process of change by which people originated from apelike ancestors. Scientific evidence shows that the physical and behavioral traits shared by all people originated from apelike ancestors and evolved over a period of at least 5 million years.

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One of the earliest defining human traits is bipedalism -- the ability to walk on two legs -- evolved over 4 million years ago. Other important human characteristics -- such as a large and complex brain, the ability to make and use tools, and the capacity for language -- developed more recently. Many advanced traits -- including complex symbolic _expression, art, and elaborate cultural diversity -- emerged mainly during the past 100,000 years.

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Humans are primates. Physical and genetic similarities show that the modern human species, Homo sapiens, has a very close relationship to another group of primate species, the apes. Humans and the great apes (large apes) of Africa -- chimpanzees (including bonobos, or so-called “pygmy chimpanzees”) and gorillas -- share a common ancestor that lived between 5 and 8 million years ago. Humans first evolved in Africa, and much of human evolution occurred on that continent. The fossils of early humans who lived between 2 and 5 million years ago come entirely from Africa.

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Most scientists currently recognize some 10 to 15 different species of early humans. Scientists do not all agree, however, about how these species are related or which ones simply died out. Many early human species -- certainly the majority of them -- left no living descendants. Scientists also debate over how to identify and classify particular species of early humans, and about what factors influenced the evolution and extinction of each species.

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Early humans first migrated out of Africa into Asia probably between 1.6 million and 2 million years ago. They entered Europe somewhat later, generally within the past million years. Species of modern humans populated many parts of the world much later. For instance, people first came to Australia probably within the past 60,000 years and to the Americas within the past 30,000 years or so. The beginnings of agriculture and the rise of the first civilizations occurred within the past 10,000 years.

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Paleoanthroplogy

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Paleoanthropology is the scientific study of human evolution and  a subfield of anthropology, the study of human culture, society, and biology. The field involves an understanding of the similarities and differences between humans and other species in their genes, body form, physiology, and behavior. Paleoanthropologists search for the roots of human physical traits and behavior. They seek to discover how evolution has shaped the potentials, tendencies, and limitations of all people. For many people, paleoanthropology is an exciting scientific field because it investigates the origin, over millions of years, of the universal and defining traits of our species. However, some people find the concept of human evolution troubling because it can seem not to fit with religious and other traditional beliefs about how people, other living things, and the world came to be. Nevertheless, many people have come to reconcile their beliefs with the scientific evidence.

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Early human fossils and archeological remains offer the most important clues about this ancient past. Thus remains include bones, tools and any other evidence (such as footprints or butchery marks on animal bones) left by earlier people. Usually, the remains were buried and preserved naturally. They are then found either on the surface (exposed by rain, rivers, and wind erosion) or by digging in the ground. By studying  fossilized bones, scientists learn about the physical appearance of earlier humans and how it changed. Bone size, shape, and markings left by muscles tell us how those predecessors moved around, held tools, and how the size of their brains changed over a long time. Archeological evidence refers to the things earlier people made and the places where scientists find them. By studying this type of evidence, archeologists can understand how early humans made and used tools and lived their environments.

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The Process of Transformation

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The process of transformation involves a series of natural changes that cause species (populations of different organisms) to arise, adapt to the environment, and become extinct. All species or organisms have originated through the process of biological evolution. In animals that reproduce sexually, including humans, the term species refers to a group whose adult members regularly interbreed, resulting in fertile offspring -- that is, offspring themselves capable of reproducing. Scientists classify each species with a unique, two-part scientific name. In this system, modern humans are classified as Homo sapiens.

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Evolution occurs when there is change in the genes (the chemical molecule, DNA) inherited from the parents and especially in the proportions of different genes in a population. The information contained in genes can change by a process known as mutation. The way particular genes are expressed – that is, how they influence the body or behavior of an organism -- can also change. Genes affect how the body and behavior of an organism develop during its life, and this is why genetically inherited characteristics can influence the likelihood of an organism’s survival and reproduction. Evolution does not change any single individual. Instead, it changes the inherited means of growth and development that typify a population (a group of individuals of the same species living in a particular habitat). Parents pass adaptive genetic changes to their offspring, and ultimately these changes become common throughout a population. As a result, the offspring inherit those genetic characteristics that enhance their chances of survival and ability to give birth, which may work well until the environment changes. Over time, genetic change can alter a species' overall way of life, such as what it eats, how it grows, and where it can live. Human evolution took place as new genetic variations in early ancestor populations favored new abilities to adapt to environmental change and so altered the human way of life.

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In everyday understanding, the "ascent of man" is a steady upward progression: Some 7 million years ago our slope-browed, knuckle-dragging ancestors break with the future chimpanzees and learn by turns to walk upright, grow bigger brains, shape bones and stones into tools -- then cap the whole process by developing language. No wonder so many modern-day Homo sapiens, skeptical that the randomness of natural selection could produce such a tidy plot line, insist there must be a creator (or at least a creative intelligence) behind the story.

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Of course not even Darwin argued for such a simplistic view of evolution, and scientists still differ over important aspects of the interaction of organisms and environment that favors some "improvements" over others. There are gaps in our understanding, and some of the widest can be found in anthropology, the human-centered discipline that was the biggest discovery in at least a half-century.

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Homo floresiensis, is a new human ancestor whose remains were found on a remote island near Java – known to be Flores Man. They appear to have been about 3 feet tall, with grapefruit-sized brains, and to have hunted skillfully and cooperatively with stone tools. Their discoverer believes they made these tools, and also employed language; other anthropologists are unpersuaded on the first point, skeptical on the latter.

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But it's the undisputed aspects of this discovery that are the most riveting. Flores Man survived into relatively modern times -- at least up to 13,000 years ago, and therefore much later than the Neanderthals of Europe, whose disappearance about 33,000 years ago had been considered the end of our archaic ancestors.

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Indeed, the skeletal remains found on Flores Island dovetail neatly with the lore of modern-day residents, the Ngadha, who say the little people were around until the arrival of Dutch trading ships in the 1500s. They were hairy and gentle, the Ngadha say; they lived in the caves and accepted bowls of food we put out for them.

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According to Michael Morwood, the University of New England anthropologist who led the excavation, Flores Man's closest probable relative among pre-humans lived about 1.7 million years ago in the formerly Soviet republic of Georgia. The journey to Java could have been accomplished over land, before the breakup of land masses, but how to explain the final leg to Flores, an island for 2.6 million years? Morwood theorizes a water crossing, probably by raft, of perhaps as little as 12 miles.

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And then the interaction of organism and environment gets really interesting. The isolation of Flores invokes the "island rule" -- in the absence of large predators, whose threats make bigness a virtue, creatures larger than rabbits become smaller as an adaptation to food scarcity. Conversely, creatures smaller than rabbits get bigger, especially if they're predators. Thus Flores was home not only to downsizing pre-humans but also to early elephants that shrank to water-buffalo size, and to little lizards that swelled into three-foot-long Komodo dragons.

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Morwood's team couldn't resist applying the nickname "Hobbit" to the hominid remains, but the story of Flores Man -- even in today's sketchy outline -- is compelling in a way that Tolkien's trilogy can't match. It arises not as the product of imagination, but as a long series of accidents -- collisions between our ancestors and environmental strictures that, contrary to previous supposition, favored shorter stature and a smaller (but perhaps better-organized) brain.

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The persistence of Flores Man into such relatively recent times is equally remarkable, and has fueled some speculation than others among our evolutionary cousins might still be living in the unexplored reaches of the planet. That possibility remains remote -- but, it must be said, a bit less remote after Morwood's discovery. Humankind's family tree has suddenly become significantly bushier, as understanding of our origins continues to evolve.

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Sequence of Transformation

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Human beings belong to the mammalian group known as Primates -- the scientific category that contains over 230 species of lemurs, lorises, tarsiers, monkeys of the Old and New World, and apes. Modern humans, early humans, and other primate species all share many similarities and have some important differences. Knowledge of these similarities and differences helps scientists to understand the roots of many human traits and the significance of each development in human evolution.

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All primates, including humans, share at least part of a set of common characteristics that distinguish them from other mammals. Many of these characteristics evolved as adaptations for life in the trees, an environment in which the earliest primates evolved. These characteristics include more reliance on sight than smell; overlapping fields of vision, allowing stereoscopic (three-dimensional) sight; limbs and hands adapted for clinging on, leaping from and swinging in the trees; the ability to grasp and manipulate small objects (using fingers with nails instead of claws); large brains in relation to body size; and complex social lives.

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The scientific classification of primates reflects evolutionary relationships among individual species and groups of species. Strepsirhine (meaning "wet nosed") primates -- of which the living representatives include lemurs, lorises, and other groups of species -- are all commonly known as prosimians. Strepsirhines are the most primitive of living primates. They share all of the basic characteristics of primates, although their brains are neither particularly large nor complex and they have a more elaborate and sensitive olfactory system (involved in the sense of smell) then do other primates.

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The earliest monkeys and apes evolved from ancestral haplorhine (meaning "dry nosed") primates, of which the most primitive living representative is the tarsier. Tarsiers were previously grouped with prosimians, but many scientists now recognize that tarsiers, monkeys, and apes share some distinctive traits, and group the three together. Monkeys, apes, and humans -who share many traits not found in other primates -- together make up the suborder Anthropoidea. Anthropoid primates are divided into New World (South America, Central America, and the Caribbean Islands) and Old World (Africa and Eurasia) groups. The platyrrhine (broad-nosed) monkeys represent the first, and the second is the catarrhine (downward-nosed) monkeys and apes. Humans belong to this second group.

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Apes and humans together make up the superfamily Hominoidea, a grouping that emphasizes the close relationship among these species. Scientists do not all agree about the appropriate classification of the families within this superfamily. Living hominoids are grouped into either two or three families: Hylobatidae, Hominidae, and sometimes Pongidae. Hylobatidae consists of the small or so-called lesser apes of Southeast Asia, commonly known as gibbons and siamangs. The Hominidae (hominids) include humans and, according to some scientists, the great apes. For those who include only humans among the Hominidae, all of the great apes, including the orangutans of Southeast Asia, belong to the family Pongidae.

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Traditionally, the term "hominid" has referred to species of humans that evolved after the split between early humans and other ape lineages. But genetic evidence, which shows chimps and humans to be more closely related genetically (and evolutionarily) to each other than to any other ape, supports placing all of the great apes and humans together in the family of Hominidae. According to this reasoning, the evolutionary branch of Asian apes leading to orangutans, which separated from the other hominid branches by about 13 million years ago, belongs to the subfamily of Ponginae. The African apes (gorillas, chimpanzees, and humans) are then classified in the subfamily called Homininae (or hominines).  And finally, the line of early and modern humans belongs to the tribe (classificatory level above genus) Hominini, or hominins.

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This classification would be true to the genetic evidence. But it tends to be confusing when learning about the subject, as many similar names (hominoid, hominid, hominine, and hominin) would apply to the different aspects of ape and human evolution. In this article the term "early human" refers to all species of the human family tree since the divergence from a common ancestor with the African apes. Popular writing often still uses the word "hominid" to mean the same thing.

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Humans as Primates

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About 98 percent of the genes in people and chimpanzees are identical, making chimps the closest living biological relatives of humans. This does not mean that humans evolved from chimpanzees, but it does indicate that both species evolved from a common ape ancestor. Orangutans, the great apes of Southeast Asia, differ genetically from humans to a greater extent, indicating a more distant evolutionary relationship.

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Modern humans have a number of physical characteristics indicative of an ape ancestry. For instance, people have shoulders with a wide range of movement and fingers capable of strong grasping. In apes, these characteristics are highly developed as adaptations for brachiation (swinging from branch to branch in trees). Although humans do not brachiate, the general anatomy of that earlier adaptation still remains. Both people and apes also have larger brains and greater cognitive abilities than do most other mammals.

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Human social life, too, shares similarities with that of African apes and other primates -- such as baboons and rhesus monkeys -- that live in large and complex social groups. Group behavior among chimpanzees, in particular, strongly resembles that of humans. For instance, chimps form long-lasting attachments with each other; participate in social bonding activities, such as grooming, feeding, and hunting; and form strategic coalitions with each other in order to increase their status and power. Early humans also probably had this kind of elaborate social life.

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However, modern humans fundamentally differ from apes in many significant ways. For example, as intelligent as apes are, people's brains are much larger and more complex, and people have a unique intellectual capacity and elaborate forms of culture and communication. In addition, only people habitually walk upright, can precisely manipulate very small objects, and have a throat structure that makes speech possible.

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The Fossil Primates

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The origin of the mammalian group primates is traced back to Plesiadapiformes, the last common ancestors of strepsirhines and other mammals. Plesiadapiformes evolved at least 65 million years ago. They were creatures similar to the modern tree shrews. The earliest primates evolved by about 55 million years ago. The first strepsirhine primates, fossil species similar to lemurs and tarsiers, evolved during the Eocene epoch (about 56 to 34 million years ago). The oldest lineages of catarrhine primates, from which monkeys and apes evolved, are known between 50 and 33 million years ago. A primate known as Propliopithecus (one lineage sometimes called Aegyptopithecus), from the Fayum fossil sites of Egypt, is an archaic-looking catarrhine, and is thought to be what the common ancestor of all later Old World monkeys and apes looked like. So Propliopithecus may be considered an ancestor, or closely related to a direct ancestor, of humans.

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Hominoids, or members of the super-family Hominoidea, evolved during the Miocene epoch (24 million to 5 million years ago). Large ape species had originated in Africa by 23 or 22 million years ago. Among the oldest known hominoids is a group of apes known by its genus name, Proconsul. Species of Proconsul had features that suggest a close link to the common ancestor of apes and humans. The ape species Proconsul heseloni lived in dense forests of eastern Africa about 20 million years ago. It was agile in the trees, with a flexible backbone and narrow chest of a monkey, yet capable of wide movement of the hip and thumb as in apes.

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Early in their evolution, the large apes underwent several radiations, periods when species originated and became more diverse. After Proconsul had thrived for several million years, a group of apes from Africa and Arabia known as the afropithecines evolved around 18 million years ago and diversified into several species. By 15 million years ago, apes had migrated to Asia and Europe over a land bridge formed between the Africa-Arabian and Eurasian continents, which had previously been separated. Around this time, two other groups of apes had evolved – namely, the kenyapithecines of Africa and western Asia (first known about 15 million years ago) and the dryopithecines of Europe (first known about 12 million years ago). It is not yet clear, however, which of these groups of ape species may have given rise to the common ancestor of African apes and humans.

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Early Australopiths

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The australopiths can be divided into an early group of species (sometimes known as gracile australopiths), which arose prior to 3 million years ago; and a later group, known as robust australopiths, which evolved after 3 million years ago. The earlier australopiths -- of which several species evolved between 4.4 million and 3 million years ago -- generally had smaller teeth and jaws. The later robusts had larger faces with large jaws and cheek teeth.

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A 5-million-year-old jaw fragment with one molar tooth, found in Kenya, and another jaw with two molars, about 4.5 million years old, may be the oldest australopith fossils. But scientists have not yet agreed on the matter since these fossils are so fragmented and do not tell us about the canine teeth or bipedal walking. Several of the early australopiths are given the genus name Australopithecus. Yet some of the oldest finds of australopith bones, dated about 4.4 million years old, have been given a different name because of their very ancient combination of apelike and humanlike traits. These fossils, first discovered in Ethiopia in 1994, are called Ardipithecus ramidus.

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By at least 4.4 million years ago in Africa, an apelike species had evolved that had two important traits, which distinguished it from other apes: (1) small canine (eye) teeth (next to the incisors, or front teeth) and (2) bipedalism--that is the ability to walk on two legs. Scientists commonly refer to these earliest human species as australopithecines, or australopiths for short. The earliest australopith species known today belongs to the genus Ardipithecus. Other species belong to the genus Australopithecus and, by some classifications, Paranthropus. The name australopithecine translates literally as "southern ape," in reference to South Africa, where the first known australopith fossils were found.

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Countries in which scientists have found australopith fossils include Ethiopia, Tanzania, Kenya, South Africa, and Chad. Thus, australopiths ranged widely over the African continent. The Great Rift Valley of eastern Africa, in particular has become famous for its australopith finds because past movements in Earth's crust in this region were favorable to environments in which bones are easily preserved and, later, to exposure of ancient deposits of fossilized bones.

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There are many ideas about why the early australopiths split off from the apes, initiating the course of human evolution. Virtually all hypotheses invoke environmental change as an important factor, specifically in influencing the evolution of bipedalism. Some well-established ideas about why humans first evolved include (1) the savanna hypothesis, (2) the woodland-mosaic hypothesis, and (3) the variability hypothesis.

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The savanna hypothesis argues that the Miocene forests of Africa became sparse and broken up between 5 and 8 million years ago due to a cooler and drier global climate. This drying trend led to the separation of an ape population in eastern Africa from other populations of apes in the more heavily forested areas of western Africa. The eastern population had to adapt to drier, open savanna environments, which favored the evolution of terrestrial living. Terrestrial apes might have formed large social groups in order to improve their ability to find and collect food and to fend off predators. The challenges of savanna life might also have promoted the rise of tool use, for purposes such as scavenging meat from the kills of predators. These important evolutionary changes would have depended on increased mental abilities and, therefore, may have correlated with the development of larger brains in early humans.

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Critics of the savanna hypothesis argue against it on several grounds, but particularly for two reasons. First, an early australopith jaw similar to australopiths afarensis has been found in Chad in west-central Africa, 2500 kilometers west of the African rift valley. This find suggests that australopiths ranged widely over the African continent and that East Africa may not have been fully separated from environments further west. Second, there is growing evidence that open savannas were not prominent in Africa until sometime after 2 million years ago.

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Criticism of the savanna hypothesis has spawned alternative ideas about early human evolution. The woodland-mosaic hypothesis proposes that the early australopiths evolved in a mosaic of woodland and grassland that offered opportunities for feeding both on the ground and in the trees. Ground feeding then favored regular bipedal activity and, eventually, the evolution of anatomical features of the hip, leg, and foot that assisted this form of locomotion.

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The variability hypothesis suggests that early australopiths experienced many changes in environment and ended up living in a range of habitats, including forests, open-canopy woodlands, and savannas. In response, their populations became adapted to a variety of surroundings. Evidence from early australopith sites, in fact, shows this range of habitats. So the unique appearance of their skeletons may have allowed them the versatility of living in habitats with many or few trees.

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Australopith Characteristics

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Most of the distinctly human physical qualities in australopiths related to their bipedal stance. Before australopiths, no mammal had ever evolved an anatomy for habitual upright walking. African apes move around their environments in a variety of ways. They use their arms to climb and to swing through the trees (known as brachiation). They knuckle-walk when on the ground, leaning on the middle parts of their fingers. And sometimes they move on two legs, as when chimpanzees feed on low branches or when gorillas show threat displays. The australopith body was devoted especially to bipedal walking. Australopiths also had small canine teeth, as compared with long canines found in almost all other catarrhine primates.

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Other characteristics of australopiths reflected their ape ancestry. Although their canine teeth were not large, their faces stuck out far in front of the braincase. Their brains were about the same size as apes' today, about 390 to 550 cubic cm (24 to 34 cubic in) but were enlarged relative to body size. Their body weight, which can be estimated from their bones, ranged from about 27 to 49 kg (60 to 108 lb.) and they stood about 1.1 to 1.5 m (3.5 to 5 ft) tall. Their weight and height compare closely to those of chimpanzees (chimp height measured standing). Some australopith species had a large degree of sexual dimorphism -- males were much larger than females -- a trait also found in gorillas, orangutans, and some other primates.

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Australopiths also had curved powerful fingers and long thumbs with a wide range of movement. Apes, in comparison, have longer, very strong, even more curved fingers – which are advantageous for hanging and swinging from branches -- but their very short thumbs limit their ability to manipulate small objects. While the fingers were longer than in modern humans, the australopith finger bones were not so long and curved as to suggest arm swinging. It is not yet clear whether these changes in the hand of early australopiths enabled them to use tools in a better way than earlier apes or even modern chimpanzees today.

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From Ape to Human

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Fossils from several different early australopith species that lived between 4 million and 2 million years ago show a variety of adaptations that mark the transition from ape to human. The very early period of this transition, prior to 4 million years ago, remains poorly documented in the fossil record, but those fossils that do exist show the most primitive combinations of ape and human features.

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Fossils reveal much about the physical build and activities of early australopiths, but little is known about surface physical features, such as the color and texture of skin and hair, or about certain behaviors, such as methods of obtaining food or patterns of social interaction. For these reasons, scientists study the living great apes -- particularly the African apes -- to better understand how early australopiths might have looked and behaved. The study of living apes, therefore, sheds light on how the transition from ape to human might have occurred.

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For example, australopiths probably resembled the great apes in characteristics such as the shape of the face and the amount of hair on the body. Australopiths also had brains and body sizes in the same range exhibited by the great apes, leading scientists to believe that the australopiths had similar mental capabilities and possibly even social structures.

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Bipedalism

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The anatomy of australopiths shows a number of adaptations for bipedalism. Adaptations in the lower body included the following: The australopith ilium, or pelvic bone, which rises above the hip joint, was much shorter and broader than it is in apes. This new shape enabled the hip muscles to steady the body during each bipedal step. The australopith pelvis overall had evolved a more bowl-shaped appearance, which helped support the internal organs during upright stance. The upper legs angled inward from the hip joints, which positioned the knees to better support the body during upright walking. The legs of apes, on the other hand, are positioned almost straight down from the hip, so that when an ape walks upright for a short distance, its body sways from side to side. The australopith foot was also reshaped, including shorter and less flexible toes than an ape's, which provided a more rigid lever for pushing off the ground during each step.

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Other adaptations occurred above the pelvis. The australopiths’ spine had an S-shaped curve, which shortened the overall length of the torso and gave rigidity and balance when standing. By contrast, apes have a relatively straight spine. The australopith skull also had an important adaptation related to bipedalism. The opening at the bottom of the skull, known as the foramen magnum, where the spinal cord attaches to the brain, was more forward than it is in apes. This position set the head in balance over the upright spine.

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Australopiths clearly walked upright on the ground, but paleoanthropologists debate about whether the earliest humans also spent a lot of time in the trees. Certain physical features indicate that they spent at least some of their time in the trees. Such features include their curved and elongated fingers and elongated arms.

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Explaining Bipedalism

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Many different explanations have been offered to account for the evolution of upright walking. Some of the ideas include: (1) freeing the hands, which was advantageous for carrying food or tools; (2) improved vision, especially to see over tall grass; (3) reducing the body's exposure to hot sun, which allowed better cooling during the day in an open landscape; (4) hunting or weapon use, which was easier with upright posture; and (5) feeding from bushes and low branches, which was easier when standing and moving upright between closely spaced bushes.

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Although none of these hypotheses has overwhelming support, recent study of chimpanzees favors the last one. Chimps move on two legs most often when feeding on the ground from bushes and low branches. Chimps today are not, however, very good at walking in this way over long distances. As the distances between trees or groves of trees became wider during drier periods bipedal behavior in pre-human populations may have become more frequent. Accordingly, a more effective bipedal gait was favored not as an adaptation to savanna living but rather as a way of crossing less favored areas of open terrain. An ability to climb trees continued to be important. This idea may currently be the best explanation for the unique adaptation of the early australopiths: a combination of long, powerful arms, slightly elongated legs, and lower limbs reshaped for upright walking over long distances on the ground.

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Small Canine Teeth

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Compared with apes, humans have very small canine teeth. Apes, particularly males, have thick, projecting, sharp canines that they use for displays of aggression and as weapons to defend themselves. By 4 million years ago, australopiths had developed the human characteristic of having smaller, flatter canines. Canine reduction might have related to an increase in social cooperation among humans and an accompanying decrease in the need for males to make aggressive displays.

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Australopithecus Anamensis

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In 1965 a research team form Harvard University discovered a single arm bone of an early human at the site of Kanapoi in northern Kenya. The researchers estimated this bone to be 4 million years old, but could not identify the species to which it belonged. It was not until 1994 that a research team, led by paleoanthropologist Meave Leakey, found numerous teeth and fragments of bone at the site that could be linked to the previously discovered fossil. Leakey and her colleagues determined that the fossils were those of a very primitive species of australopith, which was given the name Australopithecus anamensis. Researchers have since found other Australopith anamensis fossils at nearby sites, dating between about 4.2 million and 3.9 million years old. The skull of this species appears apelike, while its enlarged tibia or lower leg bone, indicates that it supported its full body weight on one leg at a time, as in regular bipedal walking.

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Australopithecus Afarensis

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Australopithecus anamensis was quite similar to another, much better-known species, australopith afarensis, a gracile australopith that thrived in eastern Africa between about 3.9 million and 3 million years ago. The most celebrated fossil of this species, known as Lucy, is a partial skeleton of a female discovered by paleoanthropologist Donald Johanson in 1974 at Hadar, Ethiopia. Lucy lived 3.2 million years ago. Several hundred fossils of this species have been described from Hadar, including a collection representing at least 13 individuals of both sexes and various ages, all from a single site that is dated 3.2 million years old.

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Researchers working in northern Tanzania have also found fossilized bones of australopith afarensis at Laetoli, a 3.6 million year old site best known for spectacular trails of bipedal human footprints (and the prints of other animals) preserved in a hardened volcanic ash. These footprints were discovered in 1978 by a research team led by paleoanthropologist Mary Leakey. They provide irrefutable evidence that australopiths regularly walked bipedally.

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The controversy about how the australopiths moved has mainly focused on Lucy's species australopith afarensis. While Lucy certainly walked upright, she stood only 3.5 feet tall and had longer, more powerful arms than most later human species, which suggests that she was also adept at climbing trees. And while the Laetoli footprints were made by bipedal humans, some scientists have argued that the imprints of the heel, arch, and toes are not exactly like those made by modern human feet. In addition, other fossils from Hadar and Laetoli come from individuals much larger than Lucy, up to 5 feet tall. This has caused controversy over whether the entire set of fossils represents one or two species, although most scientists accept the single-species idea since large and small adults, probably male and female, occurred together at the same site at Hadar.

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Another controversy arises from the claim that australopith. afarensis was the common ancestor of both later australopiths and the modern human genus, Homo. While this idea remains a strong possibility, the similarity between australopithecus afarensis and another australopith species -- one from southern Africa, named Australopithecus africanus -- makes it difficult to decide which of the two species gave rise to the genus Homo.

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Australopithecus Africanus

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Australopithecus africanus thrived in what is now the Transvaal region of South Africa between about 3.5 million and 2.5 million years ago. The anatomist Raymond Dart described this species -- the first known australopith -- on the basis of a fossil discovered in 1924 at Taung, South Africa. For two decades after this discovery, almost no one in the scientific community believed Dart's claim that the skull came from an ancestral human. In the late 1930s and 1940s, teams led by paleontologist Robert Broom unearthed many more australopith skulls and other bones from the Transvaal sites of Sterkfontein and Swartkrans.

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Australopithecus africanus generally had a more globular braincase and less primitive-looking face and teeth than did Australopithecus afarensis. Thus some scientists consider the southern species of early australopith to be a likely ancestor of the genus Homo. According to other scientists, however, Australopithecus africanus had facial features that mark it on the path to the robust australopiths found later in the same region. Some recent finds from the Transvaal site of Sterkfontein indeed have begun to blur the distinction between the early australopiths and the later robust species. In 1998 a research team led by South African paleoanthropologist Ronald Clarke unearthed an almost complete early australopith skeleton at Sterkfontein. Although it may prove to be a new species, this important find may resolve some of the questions about where Australopithecus africanus fits in the story of human evolution.

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The Later Australopiths

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By 2.7 million years ago, the robust australopiths had evolved. The robust australopiths represent an intriguing group of early humans because they survived for a long time and were quite common compared to other early human species. They had adaptations that differed from the larger-brained populations of Homo who lived at the same time, but then mysteriously became extinct by one million years ago.

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Although the word "robust" originally referred to the larger body once believed to exist in these australopiths, they are now known to have been roughly the same size as australopith afarensis and australopith africanus. Instead, "robust" accurately describes the very massive molar teeth, face, and skull muscle markings that characterized these species. The robust australopiths had megadont cheek teeth -- broad, thick-enameled molars and premolars -- which formed a flattened and worn surface. Their incisor teeth, by contrast, were small. An expanded, flattened, and more vertical face accompanied this emphasis on the back teeth. The combination of broad molars and large face was effective in absorbing the stresses of strong chewing. Along the top of the head was a sagittal crest, a raised area of bone along the skull's midline from front to back, where thick muscles that moved the jaw up and down were attached.

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The bars of bone along each side of the skull (the zygomatic arches) were positioned far to the side, which allowed huge openings for the chewing muscles near where they attached to the lower jaw. Altogether, these traits indicate very powerful and prolonged chewing of food. A similar expansion in the chewing structures can be seen in other groups of plant-eating animals. Microscopic wear on the teeth of paranthropus robustus and paranthropus boisei appear to support the idea of a vegetarian diet. It is thought that the robust australopiths had a diet consisting of tough, fibrous plant food, such as seed pods and underground tubers. However, chemical studies of fossil bones suggest that the southern species may also have eaten animals.

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Because they share the features of heavy chewing, the robust australopiths appear to represent a distinct evolutionary group of early humans. Many paleoanthropologists have linked the robust species together with a unique genus name, Paranthropus (the name originally given to the southern robust species). This classification implies that the first robust species, paranthropus aethiopicus, became separated from the other australopiths and then evolved into paranthropus boisei and paranthropus robustus (the other two robust species). Other researchers have kept the robust species within the genus Australopithecus, stating that the eastern forms (A. aethiopicus and A. boisei) evolved their massive teeth from the early australopiths of the region (perhaps A. afarensis), whereas the southern species (robustus) evolved independently from A. africanus. If this type of parallel evolution occurred, the robust species would form two separate side branches of the human family tree. Due to alternative views such as this, the robust species are often known by more than one name (such as Australopithecus boisei and Paranthropus boisei).

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Paranthropus Aethiopicus

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The earliest known robust species, Paranthropus aethiopicus, had evolved in eastern Africa by 2.7 million years ago. In 1985 at West Turkana, Kenya, paleoanthropologist Alan Walker discovered the fossil skull that defined this species. It became known as the "black skull" because of the color it had absorbed from minerals in the ground. The skull, dated 2.5 million years old, had a tall sagittal crest toward the back of its cranium and a face that projected far outward from the forehead. Paranthropus aethiopicus shares some primitive features with Australopithecus afarensis -- that is, features that originated in the earlier East African australopith.  This may indicate that paranthropus aethiopicus evolved from Australopithecus afarensis.

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Paranthropus Boisei

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Paranthropus boisei, the other well-known East African robust australopith, lived over a large geographic range between about 2.3 million and 1.2 million years ago. In 1959 Mary Leakey discovered the first fossil of this species -- a nearly complete skull at the site of Olduvai Gorge in Tanzania. Paleoanthropologist Louis Leakey, husband of Mary, named the new species Zinjanthropus boisei (Zinjanthropus translates as "East African man"). This skull, which is dated to 1.8 million years ago, has the most specialized features of all the robust species. It has a massive, wide, and dished-in face that was capable of withstanding extreme chewing forces, and its molars are four times the size of those in modern humans. Since the discovery of Zinjanthropus, now recognized as an australopith, scientists have found great numbers of paranthropus boisei fossils in Tanzania, Kenya, and Ethiopia.

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Paranthropus Robustus

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The southern robust species, which has the descriptive name Paranthropus robustus, lived between about 1.8 million and 1.3 million years ago in the Transvaal, the same region that was home to australopith africanus. In 1938 Robert Broom, who had found many australopith africanus fossils, bought a fossil jaw and molar that looked distinctly different from those in australopith africanus. After finding the site of Kromdraai, from which the fossil had come, Broom collected many more bones and teeth that together convinced him to name a new species, which he called Paranthropus robustus (Paranthropus meaning "beside man").

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The Fate of the Later Australopiths

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The youngest fossils of robust australopiths are about 1.2 million years old, which suggests that they became extinct by around then. At about that time world climate began to fluctuate in a different pattern, and that may have reduced the food supply on which the robust species depended. Interaction with other early humans, such as Homo erectus, has been suggested as another reason for their extinction, although no compelling evidence exists of direct contact between these species. Competition with several other species of plant-eating monkeys and pigs, which thrived in Africa in the time, may have been an even more important factor. Still, the reasons why the robust australopiths became extinct, after such a successful time, are unknown.

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Fossil Find Improves Knowledge of Human Origins

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New found fossils from Ethiopia are giving scientists a clearer glimpse into the murky origins of a hominid species that was an important link in the evolution of ape to man. The 4-million-year-old fossils belong to Australopithecus anamensis, the earliest known member of Australopithecus, the genus right before our own, Homo.

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The new bones which include a femur, several teeth and the largest jaw fragment ever recovered from any hominid - were discovered last December 2005 in the Middle Awash valley of Ethiopia, a region well-known for its rich deposit of hominid fossils. The fossils were found sandwiched between sediment layers containing the fossils of an earlier species, Ardipithecus ramidus, and the geologically younger Australopithecus afarensis.

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This is the first time these three species have been found together in one geographic location and in such a tight chronological order, scientists say.

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Filling in the Gaps

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The Middle Awash valley of Ethiopia has the longest and most continuous record of human evolution of any place on Earth. Scientists have found the fossils of nearly 250 hominid specimens embedded within more than a mile of stacked sediments representing time periods that stretch back 6 million years.

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The fossils of Ar. ramidus, Au. anamensis and Au. afarensis follow on the heels of one another in Middle Awash’s sediment layers - appearing at roughly 4.4 million, 4.2 million and 3.6 million years ago, respectively - allowing scientists to accurately pinpoint the time when Australopithecus first appeared.

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“The origins of Australopithecus have always been tricky, but now we have enough fossil evidence to indicate that the first occurrence of Australopithecus occurred 4.2 million years ago.  Since their remains don’t overlap, scientists think the three species are directly related, evolving one from the other, rather than being cousins that shared a common ancestor.“ This discovery fills the gap between Ardipithicus and Australopithecus,” said study team member Tim White, an anthropologist at the University of California, Berkeley.

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“Here is one place on Earth where you have 12 separate sediment layers, one stacked on top of another, whose fossils have filled in many of the gaps in human evolution over the years.  “Many of the links are no longer missing.”

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Ape to Man

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The story of human evolution can be divided into three distinct phases, beginning with our split from the common ancestor we shared with chimpanzees 8 million to 6 million years ago.  Each phase lasted for millions of years and was dominated by a separate genus; each genus was composed of numerous species.

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* The oldest genus is Ardipithecus, of which Ar. ramidus was the last member.

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* Australopithecus came next. This genus began with Au.anamensis and  includes Au. Afarensis of “Lucy “ fame.

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* Lastly is Homo, the genus containing Homo erectus, Neanderthal, The Hobbit and us – Homo sapiens.

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Human-Neanderthal Link

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A skull found in a cave in Romania includes features of both modern humans and Neanderthals, possibly suggesting that the two may have interbred thousands of years ago.

Neanderthals were replaced by early modern humans. Researchers have long debated whether the two groups mixed together, though most doubt it. The last evidence for Neanderthals dates from at least 24,000 years ago.

The skull bearing both older and modern characteristics is discussed in a paper by Erik Trinkaus of Washington University in St. Louis. The report appeared in January 2007 issue of Proceedings of the National Academy of Sciences.

The skull was found in Pestera cu Oase — the Cave with Bones — in southwestern Romania, along with other human remains. Radiocarbon dating indicates it is at least 35,000 years old and may be more than 40,000 years old.

The researchers said the skull had the same proportions as a modern human head and lacked the large brow ridge commonly associated with Neanderthals. However, there were also features that are unusual in modern humans, such as frontal flattening, a fairly large bone behind the ear and exceptionally large upper molars, which are seen among Neanderthals and other early hominids.

"Such differences raise important questions about the evolutionary history of modern humans," said co-author Joao Zilhao of the University of Bristol, England.

It could reflect a case in which ancient traits reappear in a modern human, or it could indicate a mixture of populations, Zilhao said. Or it simply may be that science hasn't been able to study enough early modern people to understand their diversity.

Dr. Richard Potts of the Smithsonian's National Museum of Natural History noted that the skull represents the earliest modern human ever found in Europe.

It's a big deal in that sense, he said, but the combination of characteristics don't necessarily indicate interbreeding between populations.

Overall there is no strong evidence for mixing of Neanderthal and modern human populations and "this doesn't add any," said Potts, who wasn't part of the research team.

None of the features cited as unusual in modern humans is exclusively Neanderthal, Potts said. Rather, they could be features passed down from earlier populations in Africa.

The field work that uncovered the skull was conducted in 2004 and 2005.

Meanwhile, a research team led by Svante Paabo of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, is trying to map the Neanderthal genome in hopes of better understanding any possible relationship to modern people.

The research was funded by the U.S. National Science Foundation, the Wenner-Green Foundation, Washington University, the Leakey Foundation, the Portuguese Institute of Archaeology, the Royal Belgian Institute of Natural Science, the Romanian National Council for Academic Research and the Foundation Fyssen.

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EPILOGUE

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It shall take human intellect to travel progressively and spend time dissecting history on an unexplainable urging of instinct into dissertation of truth based on most reasonable and reliable references through the compiled historical records. This endeavor may not be grossly mistaken as anti-religious initiatives but instead taken as a plain language in the partial recovery of truth. It must be understood however, that every mankind has their own identity and defined role without prejudice to good works and sacrifices rendered by those who were ahead us and be known exactly what they wished to be and not beyond.

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The writer just wish to share the great elation – a feeling of jubilation and encouragement that took a day to simmer down when polishing this manuscript happened to read the Episcopal Introduction of the Bible published by Claretian Publications (1988), particularly “Big Bang and not Creation” the origin of our planet on pages 07 to 09. It came to a perception that this group of humans conducts their studies in searching for the factual truth, the way ancient Essene Society had undertaken. The recovery of truth. Somehow feel naïve for lack of endeavor and initiative to breakthrough from the realm of religious ambiguities where their entity happened to be a pillion and most likely, unwilling to rock the boat.

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Indeed true, if one is heir of a very huge old traditional house has no ability to restructure it alone. The need of community efforts and assistance to rebuild and rig all sides to prevent the collapse. All members of the community should be vigilant enough to see all unsound and unsuitable components be replace giving an outmost emphasize to the restoration of a new and stable foundation. But how soon shall it take to initiate the move? The needs of world communities, through the effort of United Nations  participation can be invited for the major restoration and refurbishment works in order that all members of the world can benefit the abode.


 Just think about it.