Re: The scientific method and the AAH

loopy (
Wed, 07 Dec 1994 02:28:24 +0700

In article <3c0s1a$>, (Pat
Dooley) wrote:

> Hairlessness a simple mutation? So how come we can just about divide
> mammals into three categories:

sure it's simple. "turn off hair" is a much simpler developmental
instruction than say "build a liver." Many humans are born quite hairy, and
they may even carry it into adulthood. We still carry the instructions for
hairiness in our genes, and sometimes it reverts.
But if you were in the business of constructing evolutionary trees you'd
realize that you cannot fixate on one trait in one species.
Traits (especially simple ones) can arise for no apparent reason.

> 1. Hairy land dwellers.
> 2. Large hairless aquatic and wallowing mammals.
> 3. Small oily haired, multi-coated semi-aquatic mammals.

there are many exceptions to these groups. Armadillos, rhinos, walruses,
sea lions, for starters. We may just be another exception.

> For a savannah animal, hairlessness is just about the stupidest mutation
> possible. It removes protection from the tropical sun; it reduces the
> efficiency of sweating, and it removes thermal insulation against
> surprisingly frigid savannah
> nights.

No, it increases the efficiency of sweating. As for keeping warm at night,
many humans do just fine sleeping in the cold; for example native people in
the Andes sleep in quite frigid temperatures. They are acclimated. See
papers by Jere Haas.

> Now, once an animal has lost its hair, it takes a lot of evolutionary
> pressure to
> get it back.

no it doesn't, as long as the instructions are still there.

> The
> savannah theory, in all its mutations, has never actually come up with a
> plausible explanation for hairlessness.

The sweaty ape hypothesis seems to explain hairlessness well, IMO.


| Lucie M. Melahn