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AAT
Lisa Christy Thomas (lthomas@owlnet.rice.edu)
18 Apr 1994 17:48:54 GMT
Hello again.
When I say that aquatic life (as in, constant or near-constant
submersion) is improbable, I am referring to the fact that, as Philip
Nicholls pointed out recently, we have not made substantial structural
adaptations to a marine lifestyle. E. Morgan uses the argument that
our skins, etc., developed in such a way as to keep us warm (that
extra layer of fat) and keep our salt levels within reason (a large
amount of eccrine glands and salty tears). But if you placed our
skeletal structure alongside those of marine mammals, it doesn't seem
to fit at all. Did we at one time have webbing between our hands and
feet? The modern versions are not effective swimming appendages,
since the hands were developed with dexterity in mind, and the feet
are platforms for (dry-land) bipedalism. Other marine mammals have
svelte, streamlined bodies, with relatively short limbs (legs, for
otters, or flippers, for seals, dolphins, etc.). This helps not only
to move through the water with greater ease, but to keep the body heat
close, so that less is lost to the limbs. Humans have very lanky
bodies in comparison. Natural our structures will reflect our primate
heritage to a greater extent than any adaptations to the water, but
surely if we spent a million years as a water-dwelling species we
would see some skeletal adaptations.
I've got to get to class now. Any comments out there (and please tell
me if I'm overlooking something obvious, I have a tendency to do that)
=)
- Lisa
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