Re: Speciation - how do you know?
Paul Crowley (Paul@crowleyp.demon.co.uk)
Sat, 19 Oct 96 21:57:06 GMT
In article <54atjd$7po@dfw-ixnews11.ix.netcom.com>
hobgot@ix.netcom.com(Robert "Robert Gotschall" writes:
> Off hand I'd think there would be a close relationship between
> skeletal and dental tissue. People living in a weightless condition
> loose bone material very quickly. As I understand it, the calcium is
> simply too valuable physiologically, to leave unused in bone. Is this
> what you mean by expensive?
Broadly, Yes. And enamel is the hardest known biological material.
It must take real energy to lay down.
> Also, I think I posted earlier, given an
> omnivorous diet and primate ingenuity, early homonids would very likely
> utilize the littoral for food gathering. However, I don't get the
> point about thick enamel. Are you suggesting that they were breaking
> open clam shells with their teeth?
No. I've answered this in a previous post. But, actually, something
like this *could* be an explanation for the extraordinary dentition
of A. boisei.
> Even relatively less sophisticated
> feeders, such as sea otters, know enough to use
> a rock for that.
Otters dive deep for the right sort of shellfish. I see hominids
taking more or less what they find in the locality. They couldn't
go too far from the coast or from fresh water resources.
> Massive dentition is more often associated with a fibrous
> vegetable diet.
Most early hominids didn't have massive dentition; it was a
reduction from ape dentition. But it was much harder. And it
stayed harder throughout the whole of hominid evolution, even
though the whole dental structure became remarkably small.
There is not the slightest indication of a tough fibrous diet.
Further the Hss gut indicates the consumption of high-protein
food; while we don't have earlier hominid guts to examine,
there is no indication of a change in diet at any time. The
change in dentition is steady and progressive in one direction.
Paul.
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