From: Charles Hixson (charleshixsn@earthlink.net)
Date: Sat Mar 15 2003 - 11:59:28 MST
Mark Walker wrote:
> ...
>
>Thanks. I agree that it seems likely that humans have gone through more
>evolutionary bottlenecks, although there is still the question of how
>pressures on phenotype relate to genome evolution--I'm thinking that to some
>extent this will depend on whether Kimura's neutral theory of molecular
>evolution is true, and to what extent. In general, though, I think people
>tend to forget that whatever the percentage difference between us and chimps
>is, it will probably be less than the difference between us and our most
>recent common ape-like ancestors. (We can probably accept as unlikely
>significant convergent evolution or horizontal transfer of genes). The
>transhumanist cash-value of this question, in my mind, is that the smaller
>the percentage difference between us and our most recent ape-like ancestor,
>the more we can hope that relatively few genetic modifications may yield
>quite big dividends.
>
>Cheers,
>
>Mark
>Mark Walker, PhD
>Research Associate, Philosophy, Trinity College
>University of Toronto
>Room 214 Gerald Larkin Building
>15 Devonshire Place
>Toronto
>M5S 1H8
>www.permanentend.org
>
There is evidence that chimpanzees have gone through a bottleneck (see
the degree of variation in their histocompatibility complexes). Someone
theorized that this was due to thier encounter with SIV. So this tells
how to search to tell whether humans have gone through a bottleneck.
Look for areas of the genome that exhibit sharply reduced variability.
I suppose that if there were just a general "we're a small group
starting out" effect, then there wouldn't be any particular area that
was restricted, but rather the variability would be restricted at all
sites, but if there were selection pressures creating the bottleneck,
then the reduction in variability woule be focused on some certain few
sites.
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