Appearance of Modern Humans

Slide 36 of 109

Paleontological discoveries and geochronology show that the pattern of morphological change in the hominid fossil record was not progressive, but abrupt (1). Primitive craniodental complexes (similar to the reconstructed last common ancestor with the African great apes) were found in nearly all species of Hominidae (2). Relative brain size increased slightly among successively younger species of Australopithecines, although many Australopithecine skulls have brain capacities no larger than those of chimpanzees. (3, 4). However, brain capacities expanded abruptly with the appearance of Homo, but within early Homo remained at about half the size of Homo sapiens for almost a million years. The fossil record indicates an accumulation of relatively rapid shifts in successive species, and certainly not any kind of gradualistic changes.

References

1. Wood B. 1992. Origin and evolution of the genus Homo. Nature 355: 783-790.

2. McHenry H.M. 1994. Body size and proportions in early hominids. Proceedings of the National Academy of Sciences of the United States of America 91: 6780-6786.

3. Dean Falk. 1998. Hominid brain evolution: looks can be deceiving. Science 280: 1714

4. Conroy, G.C., G.W. Weber, H. Seidler, P.V. Tobias, A. Kane, and B. Brunsden. 1998. Endocranial capacity in an early hominid cranium from Sterkfontein, South Africa. Science 280: 1730-1731.