Wet clothes and big bodies... Was:re: AAT, a method to falsify
Bill Burnett (bbur@wpo.nerc.ac.uk)
Thu, 12 Oct 1995 12:03:44
H. M. Hubey writes:
Concerning the efficacy of fur...
>>downed navy pilot, or overboard seaman/officer, can survive while
>>dressed, while conserving energy (activity makes matters _worse_ in
>Does it make much difference that he's dressed if his clothes
>are soaked? What are you saying?
Yes it does, clothes reduce water flow over the skin and hence cooling (ask
any survival instructor). Fur works in the same way, but also by trapping an
insulating layer of air (ask any polar bear...). So really good fur is like a
drysuit. No water is warm enough for fur to be a problem shedding heat.
Even ignoring the models physics gives us, I think the whole point with fur
has often been missed and stares us in the face... The greater diversity of
aquatic mammals HAVE fur. WHY might even be irrelevant to this argument.
Only the truly marine mammals, the whales, dolphins and sirenians, are
hairless (caveat: Manatees have whiskers, does that count? :-)) The groups
which come ashore to pup or spend any time at all on land have fur. Why should
an AA be any different? The AAT has to look beyond merely being partially
aquatic to explain hairlessness.
And with regard to cold nights on the savannah...
>> Situations would be worse for a small hominid--higher surface to
>>volume ratio.
>Yes, it would be different. Then it would behoove the animal
>to get large, wouldn't it? Actually, it would be improve the
>chances of the hominid if it got larger. Now that's another
>point for AAT, isn't it? Why did the savannah hominids get
>larger, to fight the lions?
Our SA/V ratio is hopeless, too many long limbs. If we're big to keep warm
we should be short and tubby. But being big (i.e. tall) IS an advantage if
you want tosee further. I think the lions are a definite (if unintentional)
red herring here... though you might see them coming from further away...
They're just not a sufficiently ravening hoard to digest an entire
protospecies every time it (theoretically) steps out of the forest. More
likely an ecological advantage lies in the enhanced ability to hunt as well as
to avoid predators. This ability, assuming it's reasonably effective (any
theories on how effective it actually was?), might also result in a higher
protein diet and a consequent phenotypic increase in size (c.f. post war
increase in height in some E. Asian countries following industrialisation and
"improved" diet.) I'm not claiming the increase is _purely_ phenotypic
(obviously, I don't think my sister would be Lucy sized on a poor diet...) but
it might make a considerable contribution.
Bill
>--
> Regards, Mark
> http://www.smns.montclair.edu/~hubey
|