Evolution

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eth. The earliest hominine remains possess canines that project slightly, but
those of all later hominines show a marked reduction in size. Also, the chewing
teeth—premolars and molars—have decreased in size over time. Associated with
these changes is a gradual reduction in the size of the face and jaws. In early
hominines, the face was large and positioned in front of the braincase. As the
teeth became smaller and the brain expanded, the face became smaller and its
position changed; thus, the relatively small face of modern humans is located
below, rather than in front of, the large, expanded braincase.

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 fou...