Re: Why is Homo sapiens hairless?

Susan S. Chin (susansf@netcom.com)
Tue, 12 Nov 1996 04:29:27 GMT

In article <327F6753.1580@paragon-networks.com>, Doug McKean
: <doug_mckean@paragon-networks.com> wrote:
<snip>
: > Could it be that hair insulates internal organs from cold AND hot climates?
: > Doug McKean

T&B Schmal (schmal@firstnethou.com) wrote:
: Doug, I don't know if you ment this or I am interpreting you incorrectly.
: Is this your thesis: That the insulative properties of hair (on zebras,
: lions,etc) actually serves to keep the heat in, not out?

: This is a real turn of the tables. I think all I have read on the subject
: assumes that the animal's metabolism is pretty much too strong for his own
: good and so he grows hair to cool off and keep out additional heat from
: the sun. But this is a waste of good metabolism. Let us say the ideal
: operating temperature is 98 degrees. In your view it would be much more
: efficient to have a natural metabolism running at, say, 90 degrees and
: then grow a layer of hair that through insulation raised it up to the
: ideal. Much less wasted energy.

This is something I learned from an introductory Phys Anthro class a long
long time ago (well, ten years), but the hypothesis was that hominids
lost their hair gradually as they left the forrested environments that
the ancestors of todays great apes lived in (modern descendants being
gorillas, chimps, and orangutan). 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...

: And getting back to the original question, I wonder what, if true, the
: implications would be for man losing his hair?

Not to be overly picky here, but humans haven't really lost all our hair.
It's just less hair. I have hair on my arms that are the color of my
skin, virtually invisible but there just the same... But that's probably
what you meant anyway...

Susan

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                                             susansf@netcom.com