Re: Adaptationism's Lessons (was Re: Evolution, "adaptation")

Bryant (
14 Sep 1996 18:02:10 -0600

In article <51ephq$>, Paul Gallagher <> wrote:

>My impression is that Williams does not accept Dawkins' ideas about the
>selection of "cultural units." Check his 1992 book.

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.

None of this speaks to your rejection of adaptationist hypotheses for
emotions like jealousy. I'm curious, if I ask politely, if you might
present an alternative hypothesis. I can certainly understand
objecting to a specific adaptationist hypothesis, but to bar discussion
of *any* adaptive significance for emotions seems unreasonable to me.

Is not the best way to test non-adaptationist hypotheses for the evolution of
emotional states to first attempt to falsify the testable adaptationist

>First, the selection coefficient at a particular locus is difficult to
>measure. At the time of Lewontin's The Genetic Basis of Evolutionary Change,
>no selection coefficient of any locus in any wild population had ever been
>measured. Thus, your definition makes adaptation testable in principle, but
>in practice almost impossible to test.

Luckily, specific selection coefficients are not required. Nor is
optimality testing. One need only come up with predictions which must be
true if the trait in question was shaped by the hypothesized selection

>Second, by not providing any definition of fitness or adaptation independent
>of selection, the statement, "adaptation is the result of selection" becomes
>a tautology, and also rather uninteresting, since it makes no reference to
>"good design" in nature, which adaptation through selection was originally
>intended to explain.

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?

>It may be the case that selection is the sole cause of adaptation,
>but is relatively trivial in the evolution of the genotype, for example, if
>most alleles are selectively neutral.

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?

I'm hopeful that our positions are not so far apart, since you agree that
selection alone can create adaptation in the face of evolution's other,
randomizing, forces (mutation & drift).

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?

>interests. Selection may be the sole cause of adaptation, but the constraints
>on the path of selection may be more interesting as determinants of form.

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

You seem to feel a distinct hostility for Dawkins in particular. How come?
I agree with your statement (which echos Williams' [1966], by the way) to
the effect that we oughtn't say a gene or trait is "for" something other
than the evolved function--that is, the fitness advantages for which it
was retained evolutionarily. I remember objecting to the same part of
Extended Phenotype (I think), in which Dawkins says that if there's a
gene "for" dyslexia, there must be one "for" reading ability.

>and causation. For example, taking an aspirin relives a tooth ache. It does not
>therefore follow that the production of prostaglandins is the cause of the
>tooth ache.

Williams uses the example of earth worms' digestive tracts not being for
the benefit of farmers. Same point. Agreed. Ecosystem ecologists still
talk in these terms, by the way. The niche is spoken of as a species'
"function," as though species evolve to exist as components in an
ecological super-organism.

>Of course, I'm probably just wasting my time here! Bryant or Wilkins will just
>reply with:
>>I find it frustrating that neo-Darwinism's critics here are apparently
>>limited to their reading of Gould, and don't even understand his
>>"alternatives" to natural selection (such as his vaulted 'allometric
>>rules of development') well enough to defend them against adaptationist
>>attack. Describing is not explaining.

Sorry that my sense of frustration offended your sensibilities. This
is, you'll note, the first time you or anybody from the Gould fan club
has bothered to delineate their position articulately. Which I do