Jenny asked:

"If animals that occupy the coldest parts of our planet such as
whales and
seals have large deposits of fat for this reason, it may have been
helpful
to humans too.  It may even explain the disposition to put the fat around
the abdomen, thereby insulating the heart and other organs.

Is there any scientific evidence in humans of differences in ability to
survive cold temperatures as a function of body fat?   I wonder if two
groups of people of similar BMI but different waist-to-hip ratios have
different capacities to cope in cold tempertures."

It is on the basis of this sort of argument that the Aquatic Ape
hypothesis was constructed (there was a popular book with this title
by a journalist, whose name I forget).  Humans have abdominal fat,
it is subcutaneous, and widely distributed.  I doubt anyone on the
list would subscribe to the Aquatic Ape theory, but it does fit the
stylized facts about human fat distribution.

On the other hand, I have seen citations that give the body fat
percentage of male Eskimos at 11.5%.  Not different from, and
perhaps even a bit lower, than other HGs in warmer climates.

Also, many individuals who carry large amounts of fat have reduced
capacity for thermogenesis and have virtually inactive brown adipose
tissue, hardly the relationship one would expect were fat depots an
Ice Age survival strategy.

In line with Jenny's question, I doubt that our ancestors beyond 15
thousand years back were fat.  The few Venus figures that might be
evidence of obesity are only of females and could have been stylized
or rare instances.  There are no cave drawings between 15,000 and
30,000 years ago of obese males or females.  It is difficult to put
on fat in a world of scarce carbohydrate and only moderate amounts
of seasonally available animal fat.  The Paleolithic activity
patterns, which mix intermittent intense activities (which release
growth hormone, an antagonist to insulin) with a high basal activity
rate would have made the attainment of obesity rare.  This is
precisely the kind of food and activity pattern that would have made
insulin resistence a useful adaptation.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Arthur De Vany
Professor
Institute for Mathematical Behavioral Sciences
3151 Social Science Plaza
Irvine, CA  92697-5100
949-824-5269
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http://www.socsci.uci.edu/mbs/personnel/devany/devany.html
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