Re: AAT a bust
(no name) ((no email))
27 Sep 95 23:39:57 GMT
In <44c3oi$5i1@ccshst05.cs.uoguelph.ca> sstinson@uoguelph.ca (Sean Stinson) writes:
[whales, small feet etc snipped]
> It might also be noted that penguins who have evolved an
>aquatic lifestyle are also bipedal in their terrestrial locomotion,
>as are polar bears.
>
Unfortunately, polar bears are not _primarily_ bipedal in terrestrial
locomotion. Further, other varieties of bear (some of which do not spend
any appreciable amount of time in the water (as compared to polar bears))
are equally bipedal. While it has been suggested here that all bears
share a common ancestor similar in behaviour to polar bears (ie
semiaquatic), this is simply speculation and doesn't serve to bolster the
argument that humans are bipedal due to a past aquatic or semiaquatic
phase in evolution - you can't support a speculation with a speculation
no matter how hard you try.
However, I would be interested to discover if anyone knows of any
references regarding the lengthening of phalanges in polar bears as
compared to other bears, or perhaps lengthened phalanges in otters etc.
This might serve to somewhat support the argument, but then again, the
last orangutan I saw had pretty long fingers! ;)
As to the penguin and its bipedal locomotion, one must remember that
birds are bipedal terrestrial locomotors anyway and penguins have simply
continued this trait rather than developing it as a consequence of
aquatic behaviours. Further, you will note that penguin hind-limbs are
drastically shortened in comparison to body size, which counters the
longer legged AA idea. I doubt penguins are a good comparison anyway,
since their swimming is more analagous to flight than to any motion used
by aquatic mammals.
Another point I would like to bring up here for those who like to
compare (either positively or negatively) humans to aquatic mammals such
as whales, dolphins etc is that these mammals have highly developed
tails which take the place of their largely vestigial hindlimbs. For the
comparison to be valid, I think we would have to stick to tailless
mammals which have adapted to an aquatic habitat.
...Kevyn Winkless.
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