Evolution Of Humans

Evolution Of Humans Human evolution is the biological and cultural development of humans. A human is any member of the species Homo sapiens, meaning “wise man.” Since at least the Upper Paleolithic era, some 40,000 years ago, every human society has devised a creation myth to explain how humans came to be. Creation myths are based on cultural beliefs that have been adopted as a legitimate explanation by a society as to where we came from. The science of paleoanthropology, which also tries to create a narrative about how humans came to be, is deeply technical. Paleoantropology is the science of the evolution of humans, and it is the base of all research in that field.

Humans have undergone many different changes during the last hundred million years, and it is the paleoanthropologists job to identify and explain these changes. In this research paper I will examine: human physical traits that define their species, human origins from pre-humans to modern humans, major discoveries and the history of human evolution, and what the future may hold as far as evolution for the human species. Homo sapiens are the only living representative of the family Hominidae. The Hominidae, or hominids are a group of upright walking primates with relatively large brains. So all humans are hominids, but not all hominids could be called human.

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Next all humans are primates. The mammalian order of primates include about 180 species of prosimians (lemur like animals), monkeys, apes, and ourselves. Primates are unusual mammals for they have evolved such distinctive traits as highly developed binocular vision, mobile fingers and toes with flat nails instead of claws, a shortened snout with a reduced sense of smell, and large brains relative to body size. If primates are unusual for mammals, humans are even more unusual for primates. We are essentially elaborated African apes.

We share almost 99 percent of our genetic material with chimpanzees. Yet we have several traits that are very different. Two legged walking, or bipedalism seems to be one of the earliest of the major hominine characteristics to have evolved. To accommodate this strange position, we have developed a specialized pelvis, hip and leg muscles, and an S-shaped vertebral column. Because these changes can be documented in fossil bone, bipedalism is seen as the defining trait of the sub family Homininae.

Much of the human ability to make and use tools and other objects stem from the large size and complexity of the human brain. Most modern humans have a braincase volume of between 79.3 and 91.5 cubic inches. In the course of human evolution the size of the brain has more than tripled. The increase in brain size may be related to changes in hominine behavior. Over time stone tools, and other artifacts became increasingly numerous and sophisticated.

It is likely that the increase in human brain size took place as part of a complex interrelationship that included the elaboration of tool use and tool making, as well as other learned skills which permitted our ancestors to be increasingly able to live in a variety of environments. The earliest hominine fossils show evidence of marked differences in body size, which may reflect a pattern of the different sexes in our early ancestors. The bones suggest that females may have been 3 to 4 ft in height and about 60 to 70 lb. in weight, while males may have been somewhat more than about 5 ft tall, weighing about 150 lb. The reasons for this body size difference are disputed, but may be related to specialized patterns of behavior in early hominine social groups.

This extreme difference between sexes appears to disappear gradually sometime after a million years ago. The third major trend in hominine development is the gradual decrease in the size of the face and teeth. All the great apes are equipped with large, tusklike canine teeth that project well beyond the level of the other teeth. The earliest hominine remains possess canines that project slightly, but those of all later hominines show a marked reduction in size. Also, the chewing teeth, the premolars and molars, have decreased in size over time.

Associated with these changes is a gradual reduction in the size of the face and jaws. In early hominines, the face was large and positioned in front of the braincase. As the teeth became smaller and the brain expanded, the face became smaller and its position changed. Thus, the relatively small face of modern humans is located below, rather than in front of, the large, expanded braincase. Evidence of immediate relatives of the human species begins about five million years ago with the Australopithecus genus and leads in to the primitive Homo genus to modern humans.

The nature of the humans evolution before that is uncertain, but scientists have hypothesized some ideas. What they do know is that between 7 and 20 million years ago, primitive apelike animals were widely distributed on the African and later on the Eurasian continents. Although many fossil bones and teeth have been found, the way of life of these creatures, and their evolutionary relationships to the living apes and humans, remain matters of strong disagreement among scientists. One of these fossil apes, known as Sivapithecus, appears to share many features with the living Asian great ape and the orangutan, whose direct ancestor it may well be. None of these fossils, however, offers convincing evidence of being on the evolutionary line leading to the hominid family generally. But they do help paint a picture of what early human relatives could have been like. The convincing fossil evidence for human evolution begins with Australopithecus.

Fossils of this genus have been discovered in a number of sites in eastern and southern Africa, and were first identified in South Africa in 1924. Earliest fossils show them existing about 3.9 million years ago, and the genus flourished until it seemed to have become extinct about 1.5 million years ago. All the australopithecines were efficiently bipedal and thus indisputable hominines. In details of their teeth, jaws, and brain size, however, they differ enough among themselves to warrant division into four species: A. afarensis, A.

africanus, A. robustus, and A. boisei. The earliest australopithecine is A. afarensis, which lived in eastern Africa between 3 and 3.9 million years ago. Found in the Afar region of what is now Ethiopia and in Tanzania, A.

afarensis had a brain size a little larger than those of chimpanzees. Some of the species possessed canine teeth somewhat more projecting than those of later hominines. No tools of any kind have been found with A. afarensis fossils. Between about 2.5 and 3 million years ago, A. afarensis apparently evolved into a later australopithecine, A.

africanus. Known primarily from sites in southern Africa, A. africanus possessed a brain similar to that of its predecessor. However, although the size of the chewing teeth remained large, the canines, instead of projecting, grew only to the level of the other teeth. As with A. afarensis, no stone tools have been found in association with A. africanus fossils.

By about 2.6 million years ago, the fossil evidence reveals the presence of at least two, and perhaps as many as four, separate species of hominines. An evolutionary split seems to have occurred in the hominine line, with one group evolving toward the genus Homo, and finally to modern humans, and the others developing into australopithecine species that eventually became extinct. The australopithecine species that eventually became extinct includes the robust australopithecines, A. robustus, that lived in southern Africa, and A. boisei, found only in eastern Africa.

The robust australopithecines represent an unusual adaptation because their principal difference from other australopithecines lies in the large size of their chewing teeth, jaws, and jaw muscles. The robust australopithecines became extinct about 1.5 million years ago. Although scientists do not agree, many believe that after the evolutionary split that led to robust australopithecines, A. africanus evolved into the genus Homo. This was a species called Homo habilis, or “handy man.” Appearing about 2.5 million years ago, the new hominid probably didn’t look terribly different from its predecessors, but it had a somewhat larger brain. And, perhaps as a result of some mental connection other hominids were unable to make, Homo habilis figured out for the first time how to make tools.

Earlier species had used tools like bits of bone for digging, or sticks for fishing termites out of their mounds (something modern chimps still do). But Homo habilis deliberately hammered on rocks to crack and flake them into useful shapes. The tools were probably not used for hunting, as scientists once thought. Homo habilis, on average, was less than 5 ft. tall and weighed under 100 lbs., and it could hardly have competed with the lions and leopards that stalked the African landscape. The hominids were probably scavengers instead, supplementing a mostly vegetarian diet with meat left over from predators’ kills.

Even other scavengers like hyenas, jackals and the such were stronger and tougher than early humans. But Homo habilis presumably had the intelligence to anticipate the habits of predators and scavengers, and probably used tools to butcher leftovers quickly and get back to safety. Their adaptations to the rigors of prehistoric African life enabled members of the Homo habilis species to survive for 500,000 years or more, and at least one group of them apparently evolved, around 2 million years ago. Around …


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