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Analysis of the data from immunological and electrophoretic examination of proteins, amino acid sequencing, nuclear DNA hybridization, mitochondrial DNA comparisons, and chromosomal banding patterns demonstrates that genealogically Pan and Gorilla group with Homo in the Homininae rather than with Pongo in the Ponginae. Genealogical trees constructed from amino acid sequence data by the parsimony method also provide evidence on the mode and tempo of molecular evolution. On retracing in these trees major steps in the ascent to Homo, the pattern of mutations observed suggests that at least twice during vertebrate progress, first in the early vertebrates and second in the basal eutherians and early primates, natural selection produced accelerated rates of molecular evolution followed later by decelerated rates. During periods of accelerated evolution the mutations in proteins such as globins and cytochrome c were concentrated at important functional sites. Stabilizing selection to preserve the functional improvements then caused the decelerated evolution. High levels of internal homeostasis was a further buffer reducing the external pressure for selection of new mutations in genes. The biomolecular evidence argues not only for relatively recent ancestral separations of Homo, Pan, and Gorilla, but also for the origin of man by anagenesis within a central population of the ancestral hominines.