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Re: tree-climbing hominids
chris brochu (gator@mail.utexas.edu)
16 Oct 1995 22:45:17 GMT
In article <hubey.813786124@pegasus.montclair.edu> H. M. Hubey,
hubey@pegasus.montclair.edu writes:
>>Semiaquatic reptiles, like crocs, have deep, flattened tails; low,
>>elongate snouts; short, stout limbs; and dorsally-projected orbits.
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>I hope you're not saying that you went back tens of millions
>of years on your time-travel machine and looked at them. If not
>then obviously exactly the same problems that bedevil the
>thinking processes of what's an aquatic/arboreal/terrestrial
>ape will bedevil them too. For a real convincing reason you'd
>still have to explain why these particular shapes would take
>place in water and not land because otherwise we'd never be
>sure that these changes that we observe now were not due
>to some historical accident but rather to fitness criteria.
Every last one of these can be explained as a direct adaptation for
swimming. The deep tail acts as a scull - remember, these things are
still using side-to-side tail sweeps for propulsion. The elongate snouts
present less resistance in the water as they capture fish. The shortened
limbs present less drag, and are also a developmental consequence of
other changes in the skeleton. The dorsally-projected orbits help the
animal see when underwater. Some of these changes have been quantified -
in particular, see Currie and Carroll's description of Hovasaurus
(Palaeontographica Africana, sometime in the early 1980's).
so there.
chris
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