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''Australopithecus'' (pronounced , ; anglicized〔the name was coined in 1925 by R.A. Dart from Latin ''australis'' "southern", Greek πίθηκος ''pithekos'' "ape"〕 australopithecine or australopith) is an extinct genus of hominids. From paleontological and archaeological evidence, the ''Australopithecus'' genus apparently evolved in eastern Africa around before spreading throughout the continent and eventually becoming extinct somewhat after two million years ago. During that time, a number of australopithecine species emerged, including ''Australopithecus afarensis, A. africanus, A. anamensis, A. bahrelghazali, A. deyiremeda'' (proposed), ''A. garhi'', and ''A. sediba''. For some hominid species of this time, such as ''A. robustus'' and ''A. boisei'', some debate exists whether they constitute members of the same genus. If so, they would be considered 'robust australopiths', while the others would be 'gracile australopiths'. However, if these species do constitute their own genus, they may be given their own name, ''Paranthropus''. ''Australopithecus'' species played a significant part in human evolution, the genus ''Homo'' being derived from ''Australopithecus'' at some time after three million years ago. Among other things, they were the first hominids to show the presence of a gene that causes increased length and ability of neurons in the brain, the duplicated ''SRGAP2'' gene.〔Reardon, Sara (2012), "The Humanity Switch", ''New Scientist'' (AU/NZ), 12 May 2012 No. 2864, pp. 10–11. ISSN 1032-1233〕 One of the australopith species eventually became the ''Homo'' genus in Africa around two million years ago (e.g. ''Homo habilis''), and eventually modern humans, ''H. sapiens sapiens''.〔Toth, Nicholas and Schick, Kathy (2005). "African Origins" in ''The Human Past: World Prehistory and the Development of Human Societies'' (Editor: Chris Scarre). London: Thames and Hudson. Page 60. ISBN 0-500-28531-4〕 ==Evolution== Gracile australopiths shared several traits with modern apes and humans, and were widespread throughout Eastern and Northern Africa around 3.5 million years ago. The earliest evidence of fundamentally bipedal hominids can be observed at the site of Laetoli in Tanzania. This site contains hominid footprints that are remarkably similar to those of modern humans and have been dated to as old as 3.6 million years. The footprints have generally been classified as australopith because that is the only form of prehuman known to have existed in that region at that time. ''Australopithecus anamensis'', ''A. afarensis'', and ''A. africanus'' are among the most famous of the extinct hominins. ''A. africanus'' was once considered to be ancestral to the genus ''Homo'' (in particular ''Homo erectus''). However, fossils assigned to the genus ''Homo'' have been found that are older than ''A. africanus''. Thus, the genus ''Homo'' either split off from the genus ''Australopithecus'' at an earlier date (the latest common ancestor being either ''A. afarensis'' or an even earlier form, possibly ''Kenyanthropus''), or both developed from a yet possibly unknown common ancestor independently. According to the Chimpanzee Genome Project, the human (''Ardipithecus'', ''Australopithecus'' and ''Homo'') and chimpanzee (''Pan troglodytes'' and ''Pan paniscus'') lineages diverged from a common ancestor about five to six million years ago, assuming a constant rate of evolution. It is theoretically more likely for evolution to happen more slowly, as opposed to more quickly, from the date suggested by a gene clock (the result of which is given as a youngest common ancestor, i.e., the latest possible date of divergence.) However, hominins discovered more recently are somewhat older than the presumed rate of evolution would suggest. ''Sahelanthropus tchadensis'', commonly called "''Toumai''", is about seven million years old and ''Orrorin tugenensis'' lived at least six million years ago. Since little is known of them, they remain controversial among scientists since the molecular clock in humans has determined that humans and chimpanzees had a genetic split at least a million years later. One theory suggests that the human and chimpanzee lineages diverged somewhat at first, then some populations interbred around one million years after diverging.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Australopithecus」の詳細全文を読む スポンサード リンク
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