Re: bipedalism and AAH

9 May 1995 18:10:02 GMT

Pat Dooley ( wrote:
: Harry Erwin writes :

: >Bipedalism is an arid-country strategy that involves maximization of the
: >search rate. Joel Brown did work on this at the University of Arizona
: >back in the 1980s.

: Objection 1: The evolution of bipedalism predated the shift to the
: savannah

Probably not. It's complementary to tree-climbing in the _wooded_ savanna.

: Objection 2: Even if bipedalism did maximise search rates, one still has
: to
: address the issue of disadvantageous intermediates. Let's clarify that by
: a
: parallel example. Being able to soar like a vulture would definitely
: maximise
: the search rate, but no primates have evolved such an ability. The problem
: is that the intermediate forms; the semi-winged non-flying primates, would

: be far more vulnerable than their ancestors to predation.

Why? It just means they need a higher tree density and spend less of
their time on the ground than their descendents.

: While the adaptations for bipedalism are not as radical as those required
: for
: flight, they are still quite dramatic, especially given the time frames
: involved.

The implication is that Kangaroo Rats cannot evolve. I've got a few on
some land I own out in California.

: Elaine Morgan does a great job in Scars of Evolution in explaining the
: adaptations
: required for bipedalism.

: Objection 3: If you want to maximise the search rate in arid country, you
: have to minimise water loss; humans are very inefficient water conservers,
: mainly due to their hairlessness and poorly regulated sweating mechanism.

Stay out of the sun at midday. I'm not talking arid as in semidesert; I'm
talking about wooded savanna and river gallery forests with access to water
sources. The adaptation doesn't have to be perfect (and won't be--see
Melanie Mitchell's work on premature convergence in genetic algorithms).

: Pat D

Harry Erwin
PhD student in comp neurosci: "Glitches happen" & "Meaning is emotional"