Re: Bipedalism and theorizing... was Re: Morgan and creationists
Gerrit Hanenburg (ghanenbu@inter.nl.net)
Wed, 25 Sep 1996 11:56:41 GMT
"John Waters" <jdwaters@dircon.co.uk> wrote:
>> While Gerrit demurred, I maintained that it would be almost
>> inconceivable that a chimp - female or male - would adopt a
>> bipedal posture while carrying a heavy infant.
In Goodall's "The Chimpanzees of Gombe" there are two instances of
chimp mothers assuming a bipedal posture while carrying an infant
(pp.438 and 556).One with the infant in ventro-ventral position and
the other in dorsal position.They seem to hold on pretty well despite
the activity that is involved.
>JW: I am sure you are right. A Chimp physiology would not be
>well suited to the bipedal carriage of a heavy infant. However,
>that's not the point. In my example, the infant would only be
>carried for a short distance. In addition, the infant would be
>very young (three days old) and therefore relatively light.
>JW: Again I am sure you are right. In the early days of the
>transition to bipedalism the lack of a proper bipedal physiology
>would have led to the onset of rapid fatigue. This would
>necessitate plenty of rest stops, when the baby would be put
>down.
This argument seems to imply that early bipedal physiology had be as
efficient as it is today in order to be adaptive.
I don't think this has to be the case.The important point is whether
or not a particular behaviour is *effective* in relation to the goal
the organism is supposed to achieve.
For example:quadrupedalism in humans is very inefficient but if it
gets you out of a burning building it's very effective and might
become an important aspect of the locomotor repertoire (assuming that
you increasingly find yourself in burning buildings).
In other words,if the pay-off is big enough efficiency is less
important.(see Rose,M.D.(1991),The process of bipedalization in
hominids.In Coppens,Y.and Senut,B.(1991),Origine(s) de la bipedie chez
les hominides.CNRS Paris,p.37-48)
Initially,early hominid bipedalism may not have been very efficient as
a means of distance travel (and may not have been used as such) but it
may have been very *effective* as a feeding adaptation (e.g.see
Hunt,K.D.(1994),The evolution of human bipedality:ecology and
functional morphology.Journal of Human Evolution 26:183-202).
If the pay-off is big enough,and the behaviour becomes an important
aspect of the locomotor repertoire,selection may futher improve on the
efficiency and in due time it may become efficient enough to be
co-opted for a different function (e.g.distance travel).
Gerrit.
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