HUMAN ORIGINS  
The fossil evidence for immediate ancestors of modern humans is divided into the genera Australopithecus and Homo, and begins about 5 million years ago. The nature of the hominine evolutionary tree before that is uncertain.

Between 7 and 20 million years ago, primitive apelike animals were widely distributed on the African and, later, on the Eurasian continents. Although many fossil bones and teeth have been found, the way of life of these creatures, and their evolutionary relationships to the living apes and humans, remain matters of active debate among scientists. One of these fossil apes, known as Sivapithecus, appears to share many distinguishing features with the living Asian great ape, the orangutan, whose direct ancestor it may well be. None of these fossils, however, offers convincing evidence of being on the evolutionary line leading to the hominid family generally or to the human subfamily in particular.

Comparisons of blood proteins and the DNA of the African great apes with that of humans indicates that the line leading to modern people did not split off from that of chimpanzees and gorillas until comparatively late in evolution. Based on these comparisons, many scientists believe a reasonable time for this evolutionary split is 6 million to 8 million years ago. It is, therefore, quite possible that the known hominine fossil record, which begins about 5 million years ago, extends back virtually to the beginnings of the human line. Future fossil discoveries may permit a more precise placement of the time when the direct ancestors of the modern African ape split off from those leading to modern people and human evolution can be said to begin.

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