SIZE AND PHYLOGENY IN HOMINOID PRIMATES

Phylogenies of the hominoid primates based on biomolecular or karyological data routinely feature an African ape-human clade that excludes orangutans, while phylogenies derived from continuous variables of the skull include the four great ape species in a single clade that excludes humans. This difference obtains whether cladistic or phenetic methods are used to estimate phylogenies. Phenetic trees based on anatomical features differ from those based on biomolecular data because of greater heterogeneity in evolutionary rates for the former among hominoid lineages. Cladistic trees from the two types of data differ primarily because similar features in gibbon and human skulls are treated as shared, derived characters in quantitative cladistic analysis, although they are size associated in gibbons and neotenic in humans. The most-parsimonious trees based on craniodental data from which such pseudoconvergences have been removed are those with an African ape-human clade. This result supports the hypothesis that man is more closely related to the chimpanzees and to the gorilla than to other living apes, as does the fossil evidence.