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Re: book reviews, parsimony and some loose ends



At 17:58 25/10/96 -0500, GO wrote:
>If bipedality were so easily evolved, and for such seemingly trivial reasons,
>then why aren't there more bipedal mammals than just humans and kangaroos
>(and a few lightweight scansorial rodents)? I maintain that bipedality in
>dinosaurs is an >abnormal vertebrate stance< necessitated by the evolution of
>the forelimbs into wings, during which the forelimbs lost their portal
>locomotor function.

I'm sorry but I find this very hard to swallow.  Are you suggesting that the
selective pressures leading to the FIRST APPEARANCE of bipedality were
related to the evolution of wings?  Surely not.  The first appearance of
bipedality must have been functional, rather than obligate - presumably
involving a shift to the hind limbs as the principal drivers in locomotion,
or a shift in function of the forelimbs to something that was certainly not
flight - perhaps grasping, perhaps climbing, who knows?  Remember that
bipedality need not be linked to flight at all (eg there are no bipedal
bats), but was necessary, I think, for the evolution of a wing structure
based on fused and reduced digits as in birds.  Thus I see bipedality
evolving before flight in birds, though when it became obligate is anybody's
guess.
--
Ronald I. Orenstein                           Phone: (905) 820-7886 (home)
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