Re: Ears under pressure. Was Re: Aquatic ape theory
Guy Hoelzer (hoelzer@unr.edu)
Thu, 26 Oct 1995 08:24:54 -0800
In article (H. M. Hubey) wrote:
> Alex Duncan <aduncan@mail.utexas.edu> writes:
>
> >In article <468c9q$72d@news.cc.ucf.edu> Thomas Clarke, writes:
>
> >>Thus while variations are random, only
> >>those that lead to increased reproduction (adaption) increase in
> >>frequency so that the population tends to evolve in the direction of
> >>those traits.
>
> >Ever heard of genetic drift? It's real. It happens frequently.
>
> You continue to use words whose meanings you don't understand
> and continue to insult people all the time by telling them
> they are ignorant but others keep quiet most of the time allowing
> the readers to see for themselves.
>
> What you have written are only words "genetic drift" blah blah.
>
> You made this mistake before a few times. Yes, the mutations/variations
> are at random. But it is either maladaptive or not. If it is maladaptive
> it will have died off so only the non_maladaptive are left. So the
> evolution is in the direction of the adaptive/advantageous traits
> Among the most advantageous/adaptive (if not the most adaptive)
> is intelligence. That is the general direction of evolution.
>
While Dr. Duncan's comment was rather terse, I agree completely with his
point. Both Thomas Clarke and H. M. Hubey are incorrect in suggesting that
only neutral or adaptive mutations will increase in frequency, possibly to
the point of fixation. In relatively small populations maladaptive
mutations can increase in frequency and even go to fixation due to random
sampling of alleles from the previous generation. This is "genetic drift",
which is much more than a meaningless term. It is an evolutionary force
that can overwhelm natural selection in relatively small populations. In
fact, population size does not have to be all that small when selection
pressures are small, as is thought to be the case for most adaptive
mutations and many maladaptive mutations. Clarke and Hubey are correct
that strongly deleterious mutations will rarely be driven to fixation by
drift. Nevertheless, it is probably not uncommon for drift to cause
maladaptive evolution.
--
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Guy Hoelzer
hoelzer@unr.edu
Dept. of Biology
University of Nevada Reno
Reno, NV 89557
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