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From: msissom@digi.lonestar.org (Marc Sissom)
Newsgroups: sci.skeptic,sci.bio
Subject: Re: Further Evolving Eyebrows
Message-ID: <1254@digi.lonestar.org>
Date: 9 Nov 90 22:17:44 GMT
References: <1371@cluster.cs.su.oz.au> <2431@anaxagoras.ils.nwu.edu> <1990Nov5.123912.15186@ioe.lon.ac.uk>
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>
>Loss of fur is a common adaptation to aquatic life (or semi aquatic
>life), consider the elephant, pig, hippoo, cetaceans (whales and dolphins).
>Indeed, Hardy first formed his theory when, on his return from a
>whaling trip, he was struck by the similarity between whale blubber
>and the human layer of subcutaneous fat.
>(Subcutaeneous fat being an aquatic adaptation against heat loss).

 Some more support for this 'aquatic period' of human development is
the fact that while all other primates are almost completely furred;
humans are the inverse, almost completely 'fur-less'. The complement
to this is that no other primates(as far as I know) have any background,
or history of an aquatic or amphibious lifestyle. Nor do they have any
affinity for activity in the water which humans certainly do. Also none
exibits this subcutaneous layer of fat.

 On the other side, is the evidence that no other primates are bipedal,
nor do they have any features to implement or enhance the development of
aerobic stamina. This supports the argument that the relatively hairless
skin with perspiration and cappillary dialation can be a very effective
radiator for a body that is running around Africa all day. A breeze across
the skin greatly enhances the value of perspiration - the draft caused by
walking/running or by the wind.

 However, with the loss of the insulating cover of fir, the skin(even with
the blood flow restricted) can now be a tremendous drain on the body heat
in other relatively cool climates. The fat layer can make up somewhat for
this loss of an insulating layer in cool conditions. Note that the fat does
not cut off the emission of heat when the body is hot because the
cappillaries are on the outside of the fat layer and provide a channel for
the flow of the excess heat.