Could the orang-utan be our closest relative?

THESE days, we tend to accept without question that humans are "the third chimpanzee". The term, coined by author Jared Diamond, refers to the notion that our closest relatives are the two chimpanzee species - the common chimp and the bonobo. But could we actually be "the second orang" - more closely related to orang-utans than chimps?

That is the controversial claim made this week by Jeffrey Schwartz of the University of Pittsburgh in Pennsylvania and John Grehan of the Buffalo Museum of Science in New York (Journal of Biogeography, DOI: 10.1111/j.1365-2699.2009.02141.x, in press)

The idea flies in the face of mainstream scientific opinion, not least a wealth of DNA evidence pointing to our close relationship to chimps. Schwartz and Grehan do not deny the similarity between human and chimp genomes, but argue that the DNA evidence is problematic and that traditional taxonomy unequivocally tells us that our closest living relatives are orang-utans.
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"There are a few features uniquely shared with chimps, but the bulk come out as [shared with] orangs," says Schwartz.

These include features of anatomy, reproductive biology and behaviour. For example, among the great apes only humans and orangs have thick tooth enamel, long hair, male facial hair, concealed ovulation, a preference for private, face-to-face mating, and an ability to construct shelters and beds. Mainstream opinion is these are due to parallel evolution.

http://www.newscientist.com/article/mg20227133.800-could-the-orangutan-be-our-closest-relative.html