Evolution Of Humans Essay Example For Students

Evolution Of Humans Essay Human evolution is the biological and cultural development of humans. A human isany member of the species Homo sapiens, meaning wise man. Since at leastthe Upper Paleolithic era, some 40,000 years ago, every human society hasdevised a creation myth to explain how humans came to be. Creation myths arebased on cultural beliefs that have been adopted as a legitimate explanation bya society as to where we came from. The science of paleoanthropology, which alsotries 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 baseof all research in that field. Humans have undergone many different changesduring the last hundred million years, and it is the paleoanthropologists jobto identify and explain these changes. In this research paper I will examine:human physical traits that define their species, human origins from pre-humansto modern humans, major discoveries and the history of human evolution, and whatthe future may hold as far as evolution for the human species. Homo sapiens arethe only living representative of the family Hominidae. The Hominidae, orhominids are a group of upright walking primates with relatively large brains. So all humans are hominids, but not all hominids could be called human. Next allhumans are primates. The mammalian order of primates include about 180 speciesof prosimians (lemur like animals), monkeys, apes, and ourselves. Primates areunusual mammals for they have evolved such distinctive traits as highlydeveloped binocular vision, mobile fingers and toes with flat nails instead ofclaws, a shortened snout with a reduced sense of smell, and large brainsrelative to body size. If primates are unusual for mammals, humans are even moreunusual for primates. We are essentially elaborated African apes. We sharealmost 99 percent of our genetic material with chimpanzees. Yet we have severaltraits that are very different. Two legged walking, or bipedalism seems to beone of the earliest of the major hominine characteristics to have evolved. Toaccommodate this strange position, we have developed a specialized pelvis, hipand leg muscles, and an S-shaped vertebral column. Because these changes can bedocumented in fossil bone, bipedalism is seen as the defining trait of the subfamily Homininae. Much of the human ability to make and use tools and otherobjects stem from the large size and complexity of the human brain. Most modernhumans have a braincase volume of between 79.3 and 91.5 cubic inches. In thecourse of human evolution the size of the brain has more than tripled. Theincrease in brain size may be related to changes in hominine behavior. Over timestone tools, and other artifacts became increasingly numerous and sophisticated. It is likely that the increase in human brain size took place as part of acomplex interrelationship that included the elaboration of tool use and toolmaking, as well as other learned skills which permitted our ancestors to beincreasingly able to live in a variety of environments. The earliest homininefossils show evidence of marked differences in body size, which may reflect apattern of the different sexes in our early ancestors. The bones suggest thatfemales 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 150lb. The reasons for this body size difference are disputed, but may be relatedto specialized patterns of behavior in early hominine social groups. Thisextreme difference between sexes appears to disappear gradually sometime after amillion years ago. The third major trend in hominine development is the gradualdecrease in the size of the face and teeth. All the great apes are equipped w ithlarge, tusklike canine teeth that project well beyond the level of the otherteeth. The earliest hominine remains possess canines that project slightly, butthose of all later hominines show a marked reduction in size. Also, the chewingteeth, the premolars and molars, have decreased in size over time. Associatedwith these changes is a gradual reduction in the size of the face and jaws. Inearly hominines, the face was large and positioned in front of the braincase. Asthe teeth became smaller and the brain expanded, the face became smaller and itsposition changed. Thus, the relatively small face of modern humans is locatedbelow, rather than in front of, the large, expanded braincase. Evidence ofimmediate relatives of the human species begins about five million years agowith the Australopithecus genus and leads in to the primitive Homo genus tomodern humans. The nature of the humans evolution before that is uncertain,but scientists have hypothesized some ideas. What they do know is th at between 7and 20 million years ago, primitive apelike animals were widely distributed onthe African and later on the Eurasian continents. Although many fossil bones andteeth have been found, the way of life of these creatures, and theirevolutionary relationships to the living apes and humans, remain matters ofstrong disagreement among scientists. One of these fossil apes, known asSivapithecus, appears to share many features with the living Asian great ape andthe orangutan, whose direct ancestor it may well be. None of these fossils,however, offers convincing evidence of being on the evolutionary line leading tothe hominid family generally. But they do help paint a picture of what earlyhuman relatives could have been like. The convincing fossil evidence for humanevolution begins with Australopithecus. Fossils of this genus have beendiscovered in a number of sites in eastern and southern Africa, and were firstidentified in South Africa in 1924. Earliest fossils show them existing ab out3.9 million years ago, and the genus flourished until it seemed to have becomeextinct about 1.5 million years ago. All the australopithecines were efficientlybipedal and thus indisputable hominines. In details of their teeth, jaws, andbrain size, however, they differ enough among themselves to warrant divisioninto four species: A. afarensis, A. africanus, A. robustus, and A. boisei. Theearliest australopithecine is A. afarensis, which lived in eastern Africabetween 3 and 3.9 million years ago. Found in the Afar region of what is nowEthiopia and in Tanzania, A. afarensis had a brain size a little larger thanthose of chimpanzees. Some of the species possessed canine teeth somewhat moreprojecting than those of later hominines. No tools of any kind have been foundwith A. afarensis fossils. Between about 2.5 and 3 million years ago, A. Shiloh by Bobbie Ann Mason Essayafarensis fossil. Nicknamed Lucy, paleoanthropologists have found out periods ofmillions of years through her, and have used that knowledge to speculate onother discoveries. Footprints, bones, teeth, etc. are all used to help piecetogether the puzzle. Human evolution may have reached a dead end, foreseeablefor a while at least. Despite the enormous changes that we have wreaked on ourenvironment, major evolutionary changes in humans will not occur in the distantfuture. Scientists dismiss the idea that the species is going somewhereunder natural selection and then describe how most successful species are stablethrough their geological lifetimes. Furthermore, given the relative pace ofcultural change and lack of isolation of human populations, there is littlechance for a new different human species. Modern understanding of humanevolution rests on known fossils, but the picture is far from complete. Onlyfuture fossil discoveries will enable scientists to fill many of the blanks inthe present picture of human evolution. Employing sophisticated technologicaldevices as well as the accumulated knowledge of the patterns of geologicaldeposition, anthropologists are now able to pinpoint the most promisinglocations for fossil hunting more accurately. In the years ahead this willresult in an enormous increase in the understanding of human biological history. BibliographyEdgar, Blake, and Johanson, Donald. From Lucy to Language. New York: Simonand Schuster, 1996. Fagan, Brian. The Journey from Eden The Peopling of OurWorld. London: Thames and Hudson, 1990. Gallagher, Richard B., Michael Murphy,and Luke ONeill. What Are We? Where Did We Come From? Where Are WeGoing? Science 14 Jan. 1994: 181-183 Gibbons, Ann, When It Comes toEvolution, Humans Are in the Slow Class. Science 31 March. 1995: 1907-1908Human Evolution. Microsoft Encarta. 1996 ed. CD-ROM Leakey, Richard. TheOrigin of Humankind. New York: Basic Books, 1994. Lemonick, Michael NewThinking on Human Evolution Time 14 March 1994: 81-87Biology