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The Hominini is a tribe of the subfamily Homininae; it comprises three subtribes: Hominina, with its one genus ''Homo''; Australopithecina, comprising several extinct genera (see taxobox); and Panina, with its one genus ''Pan'', the chimpanzees (see the evolutionary tree below). Members of the human clade, that is, the Hominini, including ''Homo'' and those species of the australopithecines that arose ''after'' the split from the chimpanzees, are called hominins; cf. Hominidae; terms "hominids" and hominins). Not all hominins are directly related to the emergence of early ''Homo''. The subtribe Hominina is the "human" branch; that is, it contains the genus ''Homo'' exclusively. Researchers proposed the taxon Hominini on the basis that the least similar species of a trichotomy should be separated from the other two. The common chimpanzee and the bonobo of the genus ''Pan'' are the closest living evolutionary relatives to humans, sharing a common ancestor with humans about four to seven million years ago.〔(【引用サイトリンク】title=Chimps and Humans Very Similar at the DNA Level )〕 Research by Mary-Claire King in 1973 found 99% identical DNA between humans and chimpanzees;〔Mary-Claire King (1973) ''Protein polymorphisms in chimpanzee and human evolution'', Doctoral dissertation, University of California, Berkeley.〕 later research modified that finding to about 94% commonality, with some of the difference occurring in noncoding DNA. == Overview == All the extinct genera listed in the taxobox are ancestral to, or offshoots of, ''Homo''. Few fossil specimens on the ''Pan'' side of the split have been found—the first discovery of a fossil chimpanzee was published in 2005; it was from Kenya's East African Rift Valley and dated to between 545 thousand years, radiometric, (kyr) and 284 kyr (via argon–argon dating). However, both ''Orrorin'' and ''Sahelanthropus'' existed around the time of the split, and so may be ancestral to both ''Pan'' and ''Homo''. In the proposal of Mann and Weiss (1996), the tribe Hominini includes ''Pan'' as well as ''Homo'', but within separate subtribes. ''Homo'' and (by inference) all bipedal apes are referred to the subtribe Hominina, while ''Pan'' is assigned to the subtribe Panina. Wood (2010) discusses the different views of this taxonomy. A source of confusion in determining the exact age of the ''Pan''–''Homo'' split is evidence of a complex speciation process rather than a clean split between the two lineages. Different chromosomes appear to have split at different times, possibly over as much as a four-million-year period, indicating a long and drawn out speciation process with large-scale hybridization events between the two emerging lineages as late as 6.3 to 5.4 million years ago according to Patterson et al. (2006). The assumption of late hybridization was in particular based on the similarity of the X chromosome in humans and chimpanzees, suggesting a divergence as late as some 4 million years ago. This conclusion was rejected as unwarranted by Wakeley (2008), who suggested alternative explanations, including selection pressure on the X chromosome in the populations ancestral to the chimpanzee–human last common ancestor (CHLCA).〔 "Patterson et al. suggest that the apparently short divergence time between humans and chimpanzees on the X chromosome is explained by a massive interspecific hybridization event in the ancestry of these two species. However, Patterson et al. do not statistically test their own null model of simple speciation before concluding that speciation was complex, and—even if the null model could be rejected—they do not consider other explanations of a short divergence time on the X chromosome. These include natural selection on the X chromosome in the common ancestor of humans and chimpanzees, changes in the ratio of male-to-female mutation rates over time, and less extreme versions of divergence with gene flow. I therefore believe that their claim of hybridization is unwarranted." 〕 ''Sahelanthropus tchadensis'' is an extinct hominid species that lived seven million years ago, very close to the time of the chimpanzee–human divergence. It is unclear whether or not it may be classed as hominin—that is, whether it rose after the split from the chimpanzees, or not. 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「Hominini」の詳細全文を読む スポンサード リンク
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