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Re: Holloway/Morgan
Ralph L Holloway (rlh2@columbia.edu)
Sun, 23 Jul 1995 13:57:14 -0400
On Sun, 23 Jul 1995, Phil Nicholls wrote:
> Hence the neurological controls over eccrine sweat allow better
> regulation (control) of the sweating process. The mechanisms is
> present in apes and monkeys but is evoked only in response to extreme
> heat stress. Hominids modified this existing system when the
> enlargement of the brain required better thermoregulation. Under
> this scenerio, Australopithecines would have been more like gorillas
> and champanzees in terms of sweating.
Thanks to Phil for re-doing this summary. I really think the nervous
sytem factor is quite important. I do hesitate to accept your reasoning
about hominids modifiying the existing sytem as a consequence of brain
enlargement, and I guess we all know that the "radiator Hypothesis",
while an interesting speculation well worthy of much more research is
still controversial, and the peer commentary from the Behavioral Brain
Sciences article make clear. Whatever the reasons, it would be useful to
reiterate just exactly as possible how human beings differ from the
large-bodied apes in thermoregulation processes. How secure is the
comparative data on numbers, ratios, of the glands, reactions to dew
points, etc., and is there a good body of information of just
within-species variation of these variable for Homo sapiens?
I ask this last question because it is a logical place to begin any
comparative study. Is the range of variation so great (or not) that ape
values in anyway overlap with our own. Iask, because Elaine Morgan's
recent post seemed to imply that there were many publications and
advances in our knowledge of these things in the '80's and 90's. I don't
have that impression.
I am aware that the change in body size and proportions between
Australopithecus and Homo (as studied through the form of the rib cage,
particularly by Leslie Aiello) might provide an alternative to the
Radiator Hypothesis, as it signals a possible reductioin in the size of
internal organs, which are also very high in terms of metabolic demands,
the implication being that the brain could afford enlargement without
building a "new" system of venous drainage.
Ralph Holloway
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