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Re: Gracile and Robust Hominids on Java
Keith (keith@pop.onwe.co.za)
Fri, 27 Dec 1996 21:51:29 GMT
phis@sprynet.com (James Howard) wrote:
>I suggest increases in testosterone drive human evolution. Human males and
>females produce more testosterone than male and female chimpanzees,
>respectively. While I think the very large increase in brain size of H. sapiens
>is due to effects resulting from latitudinal migrations, small increases in
>testosterone over time could cause small increases in brain capacity. This
>effect may be seen today as the "Flynn Effect." In a "position locked"
>situation, such as Java, it is very possible that increases in skull mass and
>cranial volume could occur in situ. That is, in a "breed and feed" area, where
>lower testosterone hominids could not flee higher testosterone hominids,
>testosterone will continue to increase. This could account for the larger brain
>capacity of the "H. erectus" specimens found in Java, compared to H. erectus
>elsewhere. It is also part of my of theory that increased testosterone
>increases vulnerability to infections. Therefore, hominids of lower
>testosterone, i.e., more gracile hominids, could arise out of the so-called H.
>erectus on Java. This could account for robust and gracile hominids, H. sapiens
>and H. erectus, on Java. The very large bodied, large brained, Neandertal,
>could arise by the same mechanism in the "position locked" environment of ice
>age Europe.
>James Howard
What evidence is there for any of your theories? Or are you saying
that because human males have larger brains this must be due to larger
titres of testosterone? Male brains may be bigger, but males are no
more intelligent (females around the thread applaud loudly).
Keith Norris
University of the Witwatersrand
South Africa
keith@gecko.biol.wits.ac.za
keith@pop.onwe.co.za
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