Molecular Phylogeny and Man's Place in Hominoidea

Abstract

Branching order among man, chimpanzee and gorilla was inferred with orangutan as an outgroup from the data of the 28S rRNA gene and of the ribosomal internal transcribed spacer recently sequenced by GONZALEZ et al. (1990). The analysis was performed by the maximum likelihood method without assuming constancy of the evolutionary rate. It was strongly suggested that chimpanzee is the closest relative of man, consistently with GONZALEZ et al.'s analysis. After establishing the branching order, the extent of rate variation among lineages was evaluated, and the branching dates were estimated for the ribosomal internal transcribed spacer by taking into account a possible rate variation. The overall evidence from the DNA sequence data accumulated up to date suggests that man separated from chimpanzee some 4-5 million years ago.