Hominid Migration (Was Re: Racial advantages? (from sci.bio.evolution))

James Howard (phis@sprynet.com)
Fri, 16 Aug 1996 14:08:29 GMT

Every new hypothesis has a beginning.

As you know, I suggest that individuals of higher testosterone force
individuals of lower testosterone away from "breed and feed" domains,
because of dominance struggles for females. Food is not the cause of
this, but food will accentuate the phenomenon. Therefore, I think
this occurred more rapidly during times of plentiful food. That is,
increased food will increase breeding fights.

Now, when food becomes scarce, populations probably move to better
feeding areas. However, scarce food reduces breeding. So, famine and
reduced breeding reduces the population. Overall, this effect may
have moved a population, but I think it is not a powerful mechanism to
cause world-wide migration. As soon as the group finds sufficient
food, the population would increase rapidly due to rapid increases in
testosterone. This would automatically start forcing low testosterone
individuals away from the group. It will reoccur whenever a migrating
group enters a breed and feed situation. It will constantly generate
population migration, because it occurs most rapidly during a time
that promotes increases in the population.

I think this describes the spread of Australopithecus from a point of
origin. It is part of my theory that the increases in testosterone
also caused part of the increase in brain size. This effect would
really begin to manifest itself if testosterone increased in the
females. That is increases in testosterone in the female population
would increase breeding activity. I think this is why human females
have reduced genital displays, but are very active sexually, compared
to chimpanzee females that produce less testosterone. One can see the
combined increase in brain size in male and female Homo erectus, and
the increase in physical size in the females of Homo erectus.

"Another correlate of brain size is a decrease in male-female body
size difference. Sexual dimorphism remained marked in the
pithecanthropines [now called Homo erectus], but it is reduced from
its Australopithecine extreme. The reduction in dimorphism was not
caused by a decrease in male size and robustness, but rather an
increase in female size." "The Stages of Human Evolution and Cultural
Origins," 3rd. ed., G.L. Brace, Prentice-Hall, 1968, page 93.

A rise in testosterone in Homo eretus females would dramatically
increase the struggle of males for females and dramatically drive Homo
erectus throughout the world. Testosterone directly affects sexual
activity in females. "Intercourse frequency, while not related to
either partner's average testosterone levels, was related to wives'
testosterone levels at their ovulatory peaks. The wives' self-rated
gratification scores correlated significantly with their own
testosterone levels. Inspection of each wife's plasma testosterone
profile across the three cycles indicated a dichotomy occurred, with
some women showing a high baseline level and others showing a low
baseline level. When wives were dichotomized on this basis, it was
found that high baseline testosterone level was significantly related
to high self-rated gratification score and to ability to form good
interpersonal relationships." Arch. Sex. Behav. 1978; 7: 157.

The formation of lengthy civilizations depends on a mechanism that
controls the effects of testosterone. It depends on the ratio of
testosterone with that of another hormone, dehydroepiandrosterone
(DHEA).

James Howard