Re: tree-climbing hominids

chris brochu (
16 Oct 1995 22:45:17 GMT

In article <> H. M. Hubey, writes:
>>Semiaquatic reptiles, like crocs, have deep, flattened tails; low,
>>elongate snouts; short, stout limbs; and dorsally-projected orbits.
>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.