Re: Adaptationism's Lessons (was Re: Evolution, "adaptation")
Paul Gallagher (m-pg0123@granny.cs.nyu.edu)
15 Sep 1996 22:28:45 -0400
mycol1@unm.edu (Bryant) writes:
>Why is this important? We were discussing genes, not memes. For the
>record, I'm not too impressed with Dawkins' take on signal evolution
>either. But most of the adaptationist notions we were discussing weren't
>Dawksinian ideas.
I owe an explanation. I was returning to a discussion I had with Wilkins
back in July on talk.origins - (the "High Table" thread, in case anyone
wants to check the archives).
>This is an interesting point. Adaptations being the traits which
>contribute to differential reproductive success because of the specific
>socio-environmental or homeostatic challenges they help overcome is
>tautological? How would you propose biologists define adaptation, then?
That's not the definition Wilkins gave. He defined adaptation solely
in terms of the selection coefficient at an individual allele. (I posted
an article about various definitions of natural selection on sci.bio.evolution.
It may still be available on http://www.dejanews.com.)
>The evolution of the genotype? I can think of genotypic causes of the
>retention of certain alleles (e.g., the heterozygote advantage of sickle
>cell in malaria-infested environments), but isn't speaking of genotypic
>evolution akin to discussing the evolution of individuals?
If by individual, you mean the gross morphology of an organism, not
necessarily. Natural selection - the differential reproductive success
of individuals - may have very little to do with the evolution of particular
DNA nucleotide sequences. It may also have very little to do with the
rates of extinction and speciation of clades (but that's another topic).
>Do you believe that most of the alleles are probably selectively
>neutral? What about the more interesting point of whether most new
>alleles (mutations) are?
That seems to be the consensus. I haven't studied the question.
>If by this you mean looking at how phylogenetic considerations (the "raw
>material" with which selection can work) limit the 'optimality' of the
>design of adaptations, I agree. If you mean that we should accept
>untestable conjectures about constraint as an *alternative* to
>adaptationist analysis of complex traits, I don't think I do. Of course,
>that would change if anybody could explain just how one tests Bauplanist
>notions.
Well, study some developmental biology - such as the Hox genes that many
people are interested in nowadays. I don't see why you consider conjectures
about developmental constraints to be untestable. Would you agree that if
developmental constraints on the direction of change for a trait exist,
adaptationist explanations of the trait lose much of their power, since the
paths open to selection are drastically limited?
Evolution and the molecular revolution, edited by Schopf and Marshall
has good coverage of several of these topics.
In any case, this no longer pertains directly to anthropology. Wouldn't it
be better to carry on this thread in sci.bio.evolution? (Not that I have
the time to carry on this thread...)
Paul
|