Re: Initial bipedalism

J. Moore (j#d#.moore@canrem.com)
Thu, 29 Jun 95 10:22:00 -0500

Vi> Yesterday, my seventh grade son turned to me out of the blue and said
Vi> "Ya know dad," (he'd been studying paleoanth as part of his social
Vi> studies course last fall) "I was just thinking: how did early man manage
Vi> while he was just evolving onto two legs? It must have been awfully
Vi> aukward while he was sort of in between." The only thing I could reply
Vi> was "this question is being hotly debated."

Vi> It seems to me this is a natural question to ask. Until we have a clear
Vi> path of evolution to bipedalism, people are going to continue to ask
Vi> this question. My son's assumption was that
Vi> we started out as quadrupeds, with an anterior centre of balance, and
Vi> thus were moving toward bipedalism by fighting against
Vi> gravity, while straining our lower backs with a permanent
Vi> stoop. It makes more sense to start with a brachiator, who
Vi> already possesses an essentially erect posture, and posterior centre of
Vi> balance, but this is not what people think of when they consider
Vi> prehominids.

Most primates, AFAIK, and certainly apes, are actually considered to
be "hindleg dominant", in other words, they do *not* have an "anterior
centre of balance" but rather are biased toward the rear. That's why
they have such long arms. Watch a couple of nature shows and you'll see
this easily. They are not bent at 90 degrees at the hips.

Actually, Alison Jolly pointed out twenty-some years ago a couple of
things that are important to keep in at least the back of one's mind,
but which rarely get specifically mentioned. One is that most primates
spend most of their time not in locomotion, but in *sitting*, and that
*postural behavior* is an important thing to think of. The other has
been pointed out by Napier (and others--don't want to slight anyone):
that as Napier says, the classification of primate locomotor behavior
involves "an abitrary segmentation of a continuous spectrum of
activity". As Jolly says, "The usual reaction of field observers is
surprise that their animals can, in fact, do *everything*." (pg. 34,
*The Evolution of Primate Behavior*, 1972, Macmillan: New York).

Vi> And that's not surprising, as
Vi> most popular texts of the last forty years contain illustrations of
Vi> prehominid candidates with a quadrupedal posture similar
Vi> to that of a baboon.
Vi> Pete Vincent

I would think that even now the most likely image of human evolution for
most people would be one of the various pictures of toddling, striding,
or running hominids, starting with the most stooped and leading to the
"good posture poster boy" image representing "us" -- extremely
misleading, at best. Yet you see variations of this supposed
progression in posture all over, even in museums... :-(

Jim Moore (j#d#.moore@canrem.com)

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