Re: Evolution, "adaptation", and what's currently adaptive
31 Aug 1996 15:24:39 -0600
In article <susansfDx0Iz0.firstname.lastname@example.org>,
Susan S. Chin <email@example.com> wrote:
>Thanks for your opinion Steve. But I was actually only addressing the
>discussions preceding this, which I don't believe you were a part of. But
>now that you've given your opinion of Bryant's position, what exactly do
>you mean by exaptation "is actually a pure adaptationist idea"? Care to
If I may, I'd like to jump in (Bryant, here). First, a note: I'm pleased
that Susan and Steve have contributed to the thread. Most threads in the
anthro phylogeny are the result of folks jumping into the middle of other
discussions. I'd really, really like to avoid another flame-war, too. :)
My opinion about why exaptation is adpatationist is that it posits that
(some) traits--even if not currently adaptive, or ever optimally functioning--
were shaped by selection for a task: they were adaptive.
Most adaptationists do not argue for current utility (though a few assume
it) and only a minority believe that optimality theory provides a
complete picture of evolutionary biology.
>I don't think that was what the thread of this discussion was about. From
>what I can tell, neither Bryant nor Len thinks this obviously. But
>rather, why should every feature that exists today "have" to have some
>adaptive or fitness value? That is the adaptationist view as I know it.
Then you probably got your view of adaptationism while reading Gould.
That was my original point in this thread.
Adaptationists assert, with considerable evidence on their side, that
natural selection, rather than genetic drift, is the ultimate source of
all adaptation. They do *not* assert that all traits were ever adaptive,
let alone currently so.
>If that is not producing from scratch, then you are saying
>adaptationists feel as Gould and Vrba do then. In which case we're
>not talking about adaptations at all, in Gould's view anyway.
Most adaptationists consider traits which were shaped by selection to be
"adaptations," regardless of whether or not those traits are currently
adaptive. I got myself in trouble earlier in this thread by bringing up the
example of sexual jealousy.
Imagine that this trait is an adaptation--that it evolved because of the
fitness benefits it afforded jealous fellows. We'll leave aside the
precursor emotion from which it was shaped, for now. Would anybody claim
that wife beating and ending up in prison is adaptive today? No. Could it
still be fairly described as an adaptation? Of course, at least by
>: First, exaptation is far from the universal paradigm of evolution, no matter how
>: much the self-aggrandizing Gould would like it to be. Second, Bryant is not
>: claiming that "just because something is adaptive today, [it must have] evolved
>: via natural selection for that reason." He has very specifically said that he is
>: not claiming that.
>I never claimed that Gould's exaptations concept is universally accepted,
>but it does offer an alternative to the adaptationist views, and helps to
>explain certain features of evolution which would otherwise seem
>inexplicable. In my experience, those who criticize Gould often do so out
>of a lack of understanding of his ideas.
:) I have read many of Gould's essays and papers and books very carefully.
Reread them, even (as I mentioned earlier in this thread). In *my*
experience, those who object to Gould's being criticized often do so out
of a serious misunderstanding of the adaptationist program. If Gould is
your only window into the adaptationist camp, your view is seriously skewed.
In my opinion. No offense intended, though.