Origin of Apes and Hominids The role of A. afarensis as the stem from which the other hominids arose is in some dispute. About 2 million years ago, after a long million year period of little change, as many as six hominid species evolved in response to climate changes associated with the beginning of the Ice Age. Two groups developed: the australopithecines, generally smaller brained and not users of tools; and the line that led to genus Homo , larger brained and makers and users of tools. The australopithecines died out 1 million years ago; Homo , despite their best efforts (atomic weapons, pollution) are still here! With an incomplete fossil record, australopithecines, at least the smaller form, A. africanus , was thought ancestral to Homo . Recent discoveries, however have caused a reevaluation of that hypothesis. One pattern is sure, human traits evolved at different rates and at different times, in a mosaic: some features (skeletal, dietary) establishing themselves quickly, others developing later (toolmaking, language, use of fire). A cluster of species developed about 2-2.5 million years ago in Africa.
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