Re: Bipedalism and theorizing... was Re: Morgan and creationists
Harry Erwin (herwin@gmu.edu)
Thu, 01 Aug 1996 20:57:15 -0400
In article <838909871snz@crowleyp.demon.co.uk>, Paul@crowleyp.demon.co.uk wrote:
> In article <4tnmsk$521@portal.gmu.edu>
> herwin@mason2.gmu.edu "HARRY R. ERWIN" writes:
>
> Paul Crowley wrote:
> > : Your scheme of things puts huge obstacles in the way of hominoid
> > : evolution. Other primates have it much easier: no adaptation to
> > : suspensory climbing; no re-adaptation to the ground. Are we really
> > : sure our ancestors weren't baboons or monkeys? (Only joking).
> >
> > We're orthograde, not pronograde, in our anatomy.
>
> But all primates are orthograde.
>
No, not all primates are orthograde. Assignment: read a good book on
primate anatomy.
>
> > : Why do you propose a suspensory stage?
> >
> > Because we've got good evidence for it (Dryopithecus).
>
> You'd have to say Dryopithecus is ancestral for it to be good
> evidence of a suspensory stage? Is this what it comes down to?
> I suggest that there is a serious conflict between your account of
> the time new motor programs take to develop and a suspensory stage.
We've also got anatomical evidence. Can you hang by your hands?
>
> A much simpler explanation for our suspensory adaptations can come
> from looking at the infantile and juvenile behaviour of the larger
> apes. Like all other primates they have to be able to cling to
> their mothers almost from birth. As they grow, there is great
> survival value in being able to clamber around smaller branches of
> trees, both to escape predators and to get food (fruit, nuts and
> buds) that the heavier adults cannot reach. While they are the
> size of gibbons their behaviour can be roughly gibbon-like.
Science is about creating a network of tested propositions that reinforce
each other. There is such a network associated with the assumption of a
suspensory stage in our evolution. It includes a good deal of hominoid
post-cranial material from the Miocene and Pliocene. It includes hominid
post-cranial material. It includes anatomy.
>
> It would follow that our ancestors were probably ground-based
> primates for 15-25 Myr. The niche is much larger. It is also
> probable that knuckle-walking is an ancient adaptation. Was there
> any post-cranial material for Ankarapithecus?
No, it does not follow. You're about 30 years out of date.
>
> Paul.
--
Harry Erwin Internet: herwin@gmu.edu
Web Page: http://osf1.gmu.edu/~herwin
49 year old PhD student in comp neuroscience (how bats do it) and adjunct lecturer for CS 211 (advanced C++)
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