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Re: To climb or not to climb



At 8:45 -0500 16/12/98, Norton, Patrick wrote:

>Dinogeorge said:
>
><I think you have this exactly backward. Most large mammals are
>non-arboreal
>quadrupeds. >
>
>You misunderstood me. You are, of course, correct that most large mammals
>are non-arboreal quadrupeds. What I said, however, was that selection
>appears to favor quadrapedal or quasi-bipedal locomotion in arboreal
>animals. Evolution has certainly shown that quadrapedism and bipedalism
>are both viable locomotive options for cursors.  My basic point is that I
>can't think of one example of an animal that has evolved an obligatory
>bipedal stance while occupying an arboreal niche (hominids came down from
>the trees before they walked fully upright.) There are no obligatory
>bipeds in the trees, except birds.  And if birds evolved obligatory
>bipedalism in an arboreal niche, they would appear to be unique example.
> I would go further and suggest that, as obligatory bipeds, dromeosaurs
>would seem to be an ecological exception if they spent much (or any) time
>in trees.

Gibbons and orangutans are obligate bipeds on the ground, though they do
use very different modes of arboreal locomotion.

I don't see how you can make the point that hominids left the trees before
being bipedal, either.  All known hominids are bipedal, even though the
feet of the early australopithecines seem to retain limited grasping
ability for tree climbing.


Laurie Nyveen                                  lawrence@dsuper.net
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