On Mon, 30 Jul 2001, Wally Day wrote:

> Granted that, in general, genetic changes happen very
> slowly, how long does it really take for a *specific*
> change to become dominant in the gene pool?

It depends on a lot of things, but an important factor is how
scattered the population is.  The more isolated breeding
populations there are, the longer it will take for any change to
become common to all of them.

> For
> instance, we can assume that all humans can tolerate
> both meat and plant foods in various ratios - some
> predisposed to eating meat, others to eating plants.
> During an extended ice age period, wouldn't natural
> selection simply eliminate most humans who exhibit a
> very low tolerance for eating meat - therefore,
> increasing the number of "meat eaters" in the general
> gene pool? Wouldn't this suggest that we should pay
> far more attention to the past 100,000 or so years
> rather than to 4 million preceeding that?

I think this is right, especially in view of recent work in
genetics indicating that all modern Europeans are descended from
a very small breeding population (No more than a few hundred) who
left Africa about 60,000 years ago to endure the rigors of the
last ice age.  This should at least be highly relevant to those
of European descent.  On the other hand, the 10,000 years or so
since the advent of agriculture are not neglible either.  They
have created very different selection pressures, but no less
intense.  This is why I think it's a mistake to consider all
humans metabolically the same.

Todd Moody
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