Re: Bipedalism and theorizing... was Re: Morgan and creationists

Harry Erwin (
Thu, 01 Aug 1996 20:57:15 -0400

In article <>, wrote:

> In article <4tnmsk$>
> "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 You're about 30 years out of date.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:
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49 year old PhD student in comp neuroscience (how bats do it) and adjunct lecturer for CS 211 (advanced C++)