Let me first respond to Lorraine Heidecker's questions of May 6.

        In 1962, JV Neel first proposed that diabetes mellitus might be
due to the presence of a "thrifty genotype" that previously had
selective advantage to  hunter gatherer populations, but was later
rendered detrimental with the advent of "civilized" or "westernized"
environments (1).   Neel further hypothesized that this "genotype" arose
as a response to periodic "feast" and "famine" conditions  that were
presumably endemic in hunter gatherer societies.  Individuals with the
"thrifty genotype" were selected, presumably because they were able to
make more efficient utilization of food resources than individuals
lacking this genotype.   Neel (2)  suggested that members of societies
who had the thrifty gene were characterized by increased response of
insulin to ingested food, leading to increased deposition of adipose
tissue.   This increase in stored energy would enable such individuals
to function better and survive longer during periods of low energy.
The thrifty gene would increase over time and survive as long as there
were marked fluctuations in food availability.    Neel did not
specifically state that the "thrifty genotype" arose exclusively as a
response to carbohydrate availability in the diet, however he did not
necessarily preclude this possibility in part (3).
        A few likely genes which may comprise portions of the "thrifty
genotype" have been identified, including the gene coding for the
protein, glycogen synthase (4), which facilitates the storage of glucose
in skeletal muscle; however, by and large, the genetic basis for
hyperinsulinemia in susceptible populations remains elusive.

                                REFERENCES

1.      Neel JV.  Diabetes mellitus: a "thrifty" genotype rendered
detrimental by "progress".  Am J Hum Genet 1962;14:353-62.
2.      Neel JV.  The thrifty genotype revisited.  In: The Genetics of
Diabetes Mellitus, J Kobberling and J Tatttersall (Eds). New York,
Academic Press, pp 283-93.
3.      Spielman RS, Fajans SS, Neel JV et al.  Glucose tolerance in two
unacculturated indian tribes of Brazil. Diabetologia 1982;23:90-93.
4.      Schalin-Jantti C et al.  Polymorphism of the glycogen synthase
gene in hypertension and normotensive subjects. Hypertension
1996;27:67-71.	


Let me respond to Ruediger Hoeflechner's questions:

In a previous post, I mentioned that the mean subsistence percentage for
animal based foods for all 181hunter gatherer societies is 56-65%; the
mode (most frequently occurring value) is 66-75%, and the median (middle
value) is 56-65%.   Ruediger asked, "does that imply that this is the
percentage of animal based foods we are adapted to?".
        This is a difficult question for which I suspect there is no
single answer.  Perhaps insulin resistant individuals will do better on
high protein, low carbohydrate diets than individuals who are more
insulin sensitive.   O'Dea  has conducted at least two preliminary
studies which is suggestive that this may be the case (1,2).   Despite
the thousands, perhaps tens of thousands of clinical trials which have
been conducted manipulating the macronutrient (protein, carbohydrate,
fat) content of diet, there are perhaps no more than a half dozen which
have examined the influence of a low fat, high protein, low carbohydrate
diet upon human health and metabolism.  This is somewhat ironic, in that
this macronutrient pattern appears to be the one which nourished mankind
for all of our time on this planet,  except fort the last 10,000 years.
        Ruediger asked, "The difference between us and our last African
ancestor cannot exceed the differences between modern Europeans and
Africans.  Isnt there still an African gut under our fair skin".
        The answer to this one is mixed, Yes and No.   Yes, our basic
physiological gastrointestinal machinery is virtually identical from one
so called "race" to the next.  However, there are some important
adaptations in gut enzyme activity and susceptibility to G.I. tract
maladies which have evolved in certain racial groups but not others.
The example of adult lactase (actually beta-galactosidases) persistence
in caucasians is perhaps the most obvious.
        Ruediger also brought up a good point regarding whether or not
data from modern hunter gatherers can be extrapolated  to ancient hunter
gathers.    In the case of plant: animal subsistence ratios; a qualified
maybe.   Remember that the average animal based subsistence ratio for
modern hunter gatherers, based on data from the Ethnographic Atlas is
56-65%, however of this amount, about 35% of the total calories are
derived from HUNTED animals and the balance from FISHED animals.   Thus,
fish make up a substantial percentage of the animal based subsistence of
modern hunter gatherers.   As previously mentioned, fish intake
increases with latitude at the expense of plant based foods.   Would
ancient hunter gatherers have included this much aquatically based foods
in their diet?  Probably not, as I have pointed out in past posts,  the
fossil record indicates that aquatic environment was generally not
exploited until about 35, 000 years ago.   So, it seems that if an
animal subsistence ratio of 56-65% would have been maintained during the
early and middle paleolithic, it probably would have had to be
maintained by an increased reliance upon hunted animal foods.    Given
the low human population density and the high ungulate density during
these times, this scenario certainly appears likely.

1.      O'Dea K.  Marked improvement in carbohydrate and lipid
metabolism in diabetic australian aborigines after temporary reversion
ot traditional lifestyle. Diabetes 1984;33:596-603.
2.      O'Dea K et al.  The effects of diet differing in fat,
carbohydrate, and fiber on carbohydrate and lipid metabolism in type II
diabetes. J Am Dietetic Assoc 1989;89:1076-86.