SUNY-Albany biologist Caro-Beth Stewart and NYU anthropologist Todd R. Disotell have proposed a controversial new model for the evolution of apes and humans, which together are called the hominoids. Stewart and Disotell argue that the ancestor of humans and the living African apes evolved in Eurasia, not Africa.
This controversial new model for the evolution of humans and apes is the cover story of the July 30th issue of Current Biology. Stewart and Disotell describe their theory in an article entitled "Primate evolution -- in and out of Africa."
Today, the lesser apes (gibbons and siamangs) and some great apes (orangutans) live in Southeastern Asia, while other great apes (gorillas and chimpanzees) live in Equatorial Africa. The fossil record indicates that apes were present in Europe and Western Asia during the Miocene Era, from about 8 to 17 million years ago. Ancestors of these ape species must have moved between the African and Eurasian land masses during their evolutionary history. According to the theory traditionally held by most paleoanthropologists, the hominoids evolved in Africa. The lesser apes and orangutans subsequently dispersed out of Africa to Eurasia at different times, leaving behind representatives of the lineage leading to the gorillas, chimpanzees and humans.
Based on a synthetic analysis of molecular, fossil, and biogeographical data for the primates, Stewart and Disotell propose instead that the lineage leading to the common ancestor of all living apes dispersed out of Africa about 20 million years ago (during the early Miocene) and then speciated into the greater and lesser Ape lineages in Eurasia. Within the past 10 million years, one of the great ape species dispersed back into Africa. This lineage eventually speciated into gorillas, chimpanzees and humans.