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''[[Australopithecus anamensis]]'', ''[[Australopithecus afarensis]]'' and ''[[Australopithecus 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, [[fossil]]s 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 platyops]]''), 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 [[molecular clock|presumed rate of evolution
''[[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.<ref name="Bower2006" />
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