The relationships of Sivapithecus and Ramapithecus and the evolution of the orang-utan.

We review here the molecular data that bear on and provide a framework for interpreting hominoid relationships. Man is shown to be most closely related to chimpanzees and gorillas among extant hominoids, with the orang-utan more distantly related to them and the gibbons more distantly still. A fossil ape, Sivapithecus meteai, shares several characters with the orang-utan and is thus probably related to it. S. meteai is part of the Middle Miocene Sivapithecus-Ramapithecus species complex, and if this group forms a valid clade then Ramapithecus must also be considered as being more closely related to the orang-utan than to man. The date of divergence of the orang-utan from the African apes and man is suggested by fossil and molecular evidence to be 10 +/- 3 Myr ago.