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Re: Speciation - how do you know?
Robert Gotschall (hobgot@sprintmail.com)
Fri, 25 Oct 1996 20:01:09 -0700
Gerrit Hanenburg wrote:
>
>
> Astronauts do not have a diet short in calcium. Osteoporosis under
> extended conditions of weightlessness does not mean that calcium is
> too valuable to leave "unused" in bone. It means that one factor
> determining bone mineral density (BMD) is the amount of stress to
> which the bones are subject.
> Another factor is hormones (ask post-menopausal women what they think
> of that)
>
> Gerrit.
Sorry, I was speaking casually. I didn't mean to imply that the dietary
influence on hominid dentition was due to calcium deficiency. Like you
say, we're all talking about mechanical stress, but not all of us are
convinced that early hominid dentition indicates an exclusive littoral
life style.
However, Paul's comment about dentition's -expense- triggered a logic
thread of its own. Actually, I was thinking about an article indicating
that a high protein diet could require excessive calcium metabolism,
leading to Ca deficiency. Since skeletal and dental calcium respond
quickly to environmental stress, I wondered if this is what he meant by
-expense-.
Hob
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