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Re: Evolution, "adaptation", and what's currently adaptive
Bryant (mycol1@unm.edu)
5 Sep 1996 10:32:09 -0600
In article <lpiotrow.411.322DFD3A@magnus.acs.ohio-state.edu>,
Len Piotrowski <lpiotrow@magnus.acs.ohio-state.edu> wrote:
>In article <50kq53$11dg@argo.unm.edu> mycol1@unm.edu (Bryant) writes:
>>[snip]
>
>>Exaptations are adaptations no longer used for the
>>original function they served.
>
>If they have no function, how can you tell they were adaptations?
Ask Gould. They're a theoretical construct, a thought experiment, meant
to illustrate the fallacy of current adaptiveness Gould sees so pervasive
in adaptationist thinking.
>>They are adaptations--just outdated ones,
>>or ones being used in novel ways that weren't originally selected for.
>
>If they have a function, then by definition they are adaptations, not
>exaptations, neh?
It's semantics. Gould says no, that adaptations only count as such if
they have current utility. Adpatationists, or many of them, say that to
the contrary, if selection shaped a trait for a given task (even if it no
longer serves that 'purpose' in the current environment), it is an
adaptation 'for' that task.
That's what I tried to communicate earlier: *If* sugar craving were an
adaptation by the latter definition--a trait that spread throughout a
species to encourage seeking out a limiting resource--it can be called
one today, even though readily available sources of sugar make it a
threat wrt tooth decay and obesity. Hence, what is adapted (adaptations)
need not be adaptive currently.
At least, that's my understanding of this.
Bryant
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