Re: Orangs as Closest

Paul Crowley (
Tue, 06 Aug 96 16:30:14 GMT

In article <> "Matthew O. Fraser" writes:

> Anyone up on the hypothesis that Orangs are humans' closest extant relative?
> I did my undergraduate training with Jeffrey Schwartz at Pitt, and he
> authored a book on the subject, but it was a couple of years after I
> graduated.

Orangs (and gibbons) are restricted to tropical rain forests without
a dry season. Normally they have to get their water without coming
down to ground, so a month or so of drought would kill off most of
them. And since they need a *continuous* rain forest to travel,
it's unlikely they ever got outside South-East Asia.

Did Schwartz deal with this aspect?

As I see it, the arboreal specialization is a one-way street; once
you're up in the high canopy, there's no way you can get down; if
there is a partly terrestrial niche, there will always be a partly
terrestrial animal occupying all, or most, of it and your arboreal
adaptations will be extremely disadvantageous. If orangs were the
closest to hominids then they must have split before the orang
became an arboreal specialist, and that's most unlikely.

The LCA of orangs and chimps/gorillas must have been a mostly
terrestrial animal to leave descendant populations in both Africa
and Asia.