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

Bryant (
9 Sep 1996 20:58:32 -0600

In article <51206t$>,
Gerold Firl <> wrote:

>2. Linkage between the eye and vision centers in the brain: if the
>presence of an eye necessitates the devotion of some portion of the
>brain to vision, then those neurons could be better used elsewhere.
>Maybe the eye has to go before those brain cells can be freed-up for
>other tasks.
>3. Injury, disease, parasite infection: eyes are more vulnurable than
>other tissues to external insult;

Nice, informed speculation, Gerold. Vertebrate brain tissue is
tremendously expensive stuff, metabolically. Evolutionary
biologists have tended to attribute eye loss across
taxa evolving in caves to simple mutation accumulation. Like drift and
constraint stories, this explanation is difficult to test, however.

Is enough known about some of the simpler creatures' neurobiology to see
if vision centers in their brains are similarly degraded as the eyes? If
the eyes, but not related brain tissues, are degraded in these creatures,
it would argue for something other than your second hypothesis. The
third seems testable against the parasitology literature.

>=-=-=-=-=-=-=-=-=-=-=-=-=-=---- Gerold Firl @ ..hplabs!hp-sdd!geroldf