From: CurtAdams@aol.com
Date: Wed Jul 17 2002 - 16:01:16 MDT
In a message dated 7/17/02 10:23:02, kevin.bluck@mail.com writes:
>However, if one thing is clear, it is that hominid fossils are very
>difficult to find, some geologies are very adverse to forming fossils at
>all, and there are huge gaps in the record.
Hominid fossils are hard to find, but we now have a lot since so much effort
has been made. There's no shortage at all from about 3-4 million years on.
> I think it is more likely that
>the direct ancestors of gorillas and whatnot simply haven't been found,
>possibly because they lived in regions where fossils did not form well
>or have been destroyed by geologic forces.
Current gorillas and chimps live in regions about as unfavorable for
fossilization as can be found - but they leave enough anyway.
>>Gibbons, incidentally, are bipeds too. It's not a human-only
>>characteristic. We're just the best at it.
>I think it is more accurate to say that gibbons are capable of
>approximating bipedality. They can also walk quadripedally with the same
>facility, which isn't saying much; they're not very good at either method.
Put them on the ground and they walk bipedally. For whatever reason, it's
easier for them.
>Humans, on the other hand, are true bipeds. We have abandoned
>quadripedality altogether. It is more difficult for us to walk on all fours
>than it is for a chimp to walk upright. Such a radical departure didn't
>"just happen".
No, but the point is that both human and chimp locomotion are reasonable
alternative developments from the descended-gibbon condition of preferred
but not obligatory bipedalism. The fossils back that up, showing all African
apes were bipeds until about 2 million years ago. The idea that human
descended
from an ape-like knucklewalker requires reversing the shift to knucklewalking
and contradicts the fossils. And it's not *that* radical - it's only
a radical shift if you start out knucklewalking.
>Possible. However, besides the regression of the upright gait, there is the
>issue of diet. Australopithecus seems to have enjoyed a human-style
>omnivorous diet, while gorillas are leaf-eaters, living on stuff that would
>be indigestible to humans. I just don't see two major attributes swinging
>one way, then back the other.
Australopithicus didn't eat a human-style diet; they ate little meat and
apparently ate high-quality plant foods like fruits, tubers (they had digging
sticks) and nuts (judging by the monster robustus jaws) Again, this is
pretty similar to the ancestral condition. Specializations happed only
once, and later - humans went to a high-meat diet, gorillas to a folivore
diet, and chimps, I'll wager, are close to the australopithicines. Gorillas
don't have any specialized enyzmology, just a fermentation chamber twice
the size of chimps.
I don't see any attributes swinging back and forth. I'm just proposing the
African apes all maintained the primitive characteristics of their group
until the Homo lineages found some new tricks and forced specialization
on the others.
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