Re: Body Hair Loss in Aquatic Mammals

Bill Burnett (
Thu, 19 Oct 1995 13:11:46

(H. M. Hubey) writes:

>Then explain why the hair from the top of the head didn't
>disappear to cool of the body when the rest of the body
>lost all its hair. There's more blood per mass going to the
>brain than probably any other place so that's where heat is
>being built up. We should have gotten some kind of
>ventilation there or at least gotten rid of the hair but that's
>where the hair remains especially on males (i.e. the head).

Actually, believe it or not, merely pumping blood at 37'C into the
brain is not going to raise the brain temperature and cause 'heat to build
up'. And if heat DOES build up in the head, then any increased blood
flow should conduct it AWAY (if 'conduct' is the right word.). Even _my_
physics is up to that.

In fact, hair on the head is adaptive for cooling. Try shaving all your hair
off and standing in hot sun (difficult this time of year in the temperate N.
hem :-)) with and without a hat and see which your brain prefers. So why
aren't we hairy all over? The best combination of bare skin for sweating and
appropriate patches of hair for shade and odour, perhaps? Unreasonable?

As for ventilation, what do you think ears are for? Clearly to let the wind
blow through. :-)