Apparently you are not clear on the difference between an implication (If A implies B then if A, necessarily B) and a presumption (If presumptively B if A, then you are entitled to assume B if A, unless there is something that rebuts that presumption.
This isn't legalism. It's baby logic.
The fact that we have a theory of evolution by natural selection at all tells us that, presumptively, traits exist or persist because they were are are adaptive. That's the effing theory.
Of course a particular trait may not be adaptive. It may be a spandrel, as I said. It may cease to be adaptive. It may be linked to an adaptive trait. It may be neutral, the result of genetic drift, sticking around because it does not harm. Not all traits are necessarily adaptive, and the existence or persistence of a trait does not imply that they are. I never said otherwise. On the contrary, I insisted on the point.
But the background assumption, the starting point, the presumption, is that adaptiveness explains the occurrence of traits. I do not not why you want to keep sticking me with the Panglossian claim that all traits are necessarily adaptive, which I have repeatedly rejected. But, to put it another way, to recognize that there are exceptions to the rule doesn't mean that the rule isn't generally valid. If you reject the presumption, you reject the theory of evolution by natural selection. That puts you out of step, to say the least, with all modern biology.
Why is this so hard to understand?
--- ravi <ravi at platosbeard.org> wrote:
> At around 23/1/07 3:43 pm, andie nachgeborenen
> wrote:
> > Ravi, the quoted statement directly contradicts
> the
> > statement with which you say you disagree:
> >
> > That the theory is true doesn't mean
> >> that it does, can (or
> >> has to) explain everything.
> >
> > Of course not. I said so. I endorsed the existence
> of
> > spandrels. That contradicts the idea that the
> theory
> > explains everything.
> >
>
> Here is what you wrote:
>
> >> Since the theory is true, the _presumption_ is
> that
> >> any given trait had an explanation saying that it
> >> originated because it was adaptive in some
> >> environment. The hypothesis that a trait is a
> >> spandrel is fallback of desperation, when no
> >> adaptationist explanation seems to be available.
>
> What I am questioning is your presumption. The
> theory of evolution is
> true, but that does not imply that every trait, by
> default, should be
> presumed to be an adaptation. While you acknowledge
> spandrels, you are
> (or seem to be) suggesting that given a trait either
> you assume it arose
> due to adaptation or you it has to be demonstrated
> that it was a
> spandrel or something else. I claim that in the
> absence of corroborating
> evidence adaptationist explanations are just another
> "just so" story of
> equal importance as other "just so" stories which
> are also part of a
> reasonably justified system of belief: the
> "spandrel" story being part
> of the shared physiological development story. In
> truth, I would say,
> both the adaptation story and spandrel story are
> sub-stories of the
> evolution story.
>
>
> > I am sorry I am getting annoyed. But some people
> here
> > are being annoying just now for no good reason.
>
>
> You are not being fair here. We, on the other side,
> could be getting
> annoyed too that you are not seeing our argument(s)
> and may be
> mischaracterising them. I am not being "annoying for
> no good reason". I
> am trying to discuss my thoughts with you. I might
> misunderstand you,
> and you might do the same, but we have to muddle
> through these things,
> together, yes? I can understand if (as Chuck put it
> appropriately with
> regards to Free Software) I am pissing on you or
> treating you
> dismissively, but I am not.
>
> --ravi
>
> ___________________________________
>
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>
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