Re: Evolution, "adaptation", and what's currently adaptive

Len Piotrowski (
Thu, 5 Sep 1996 14:26:48 GMT

In article <> Stephen Barnard <> writes:


>You must be joking.

You're right! I am joking.

>Either that or you don't know what you're talking about.

That's possibly true as well!

>kinds of molluscs have eyes. Some, such as scallops, have lots of eyes. Snails are

Not all eyes are the same. Perhaps some gastropods haven't any eyes. I bow
to a mollusk expert!

> What do you think are on the ends of those stalks? Eyes.

Couldn't say this is true, but I presume what is at the ends of those stalks
is sensitive to light, at least as measured by my own experience, OKay?

> Octopuses, which
>are closely related to molluscs, have superb eyes. (I'm pretty sure that Firl knows all

"Octopuses" related to mollusks? I wouldn't know about that, or the nature of
Firl's expertise. Sometimes I wonder though.

>The mere fact that so many phyla have independently evolved eyes -- and many different
>types of eyes -- very strongly suggests that eyes are an extremely important adaptive
>characteristic for mobile animals in a transparent lighted medium.

I think I disagreed with the functionalist argument as method, not with any
facts of adaptive importance.

>The path from no eyes to eyes is quite plausible.

... but just so!

> First a patch of light-sensitive
>cells develop.

... first step on the slippery slope, the need for a patch ...

>Then this patch forms a cavity,

... followed by the need for a cavity ...

>which is better able to resolve the
>direction of the light source.

... culminated by the need to resolve the light source.

>Then the cavity closes over on itself and a crude
>pinhole lens forms,

Another need to fold the cavity ...

>which allows for the resolution of shapes.

... and the need for resolution of shapes.

> (I'm taking about simple
>eyes -- not compound eyes like insects have.) Then we're off to the races. We get a
>better lens, the iris, the foveated retina, stereo vision, color vision, etc. All of
>these are incremental improvements.

I don't doubt the historicity of your museum of " incremental improvements." I
doubt the efficacy of the functional method used to account for each of their
appearances and the purpose of the final system.

>How do you suppose all these phyla got eyes?

I don't know how exactly these myriad series of historically related
increments came about. Do you?

>Did genetic drift miraculously produce
>them independently.

I don't know. Do you believe that one proto-eye was ancestral to all eyes?

>Is there some essential "eyeness" at work in the universe? Did
>some Creator decide it was a good idea? Let's hear a plausible explanation that doesn't
>involve adaptation.

I don't know of a plausible explanation for "eyeness." Your "incremental
steps" form a nice story, but hardly substitutes for understanding. Maybe the
snail's eye did arise just the way you claim. I don't doubt the "forces of
evolution" playing such a role. I question the methodological structure of
functionalism as a plausible explanation for each and every manifestation of
the steps of "eyeness."