Re: Why is Homo sapiens hairless?
Paul Crowley (Paul@crowleyp.demon.co.uk)
Wed, 13 Nov 96 16:36:08 GMT
In article <susansfE0qpt3.6M7@netcom.com>
susansf@netcom.com "Susan S. Chin" writes:
> . . Once this bipedal ape was out in the
> open, not necessarily a savannah, but not a covered arboreal setting
> either, the need for heat loss was such that selection favored loss of
> hair which apes living in forrested environments still have. Makes sense
> to me...
But hair insulates from the heat of the sun; and then there's the
cold at night, the thorns, the poison ivy . . . And why should
the need for heat loss be so compelling? What was waddling little
Lucy doing that needed such energy? And some more questions:
Why is it retained on the head?
Why do males have more body hair than females and children?
Why do babies have virtually none at all?
What relationship does its loss have to sweating?
Why did the sebaceous glands (formerly for oiling the hair) not
atrophy, but become gigantic after puberty, especially in males?
Why was body hair never recovered?
Let's me state my slant on the AAT: Lucy lived in a warm, over-
cast location by the non-tidal Red sea, so she did not get cold
at night. On most days she was in and out of the water getting
shellfish; a fur coat would be a drag; but worse, drying it out
every time would chill her to the bone. She often took refuge
from the sun and the heat by going into the water, so she needed
protection on her head. Males tended more to be on guard on the
landward side, and to forage in the local forests and were not so
much in the sea, so their loss of body hair is less complete.
Lucy put her babies on their backs on rocks, open to rain and
spray. Before they learned to sit up, any head hair would get
damp and cause chills.
At sea level the area was hot and humid, but away from the coast
it was mountainous. Climbing them was strenuous and an effective
method of heat loss was essential. This was sweating, which was
more efficient without the hair. The diet was high in salt and
protein; both needed a high consumption of water. Males tended
to sweat heavily and this resulted in a layer of salt on the
skin; their large sebaceous glands helped protect against this.
(Let me concede that this last sentence might be thought to
contain a small element of speculation. ;)
Hair was never recovered, because this way of life was the
predominant one for all hominids up to near-historical times,
as evidenced by the massive shell middens on all raised coasts.
Paul.
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