Gracile and Robust Hominids on Java

James Howard (
Mon, 23 Dec 1996 20:00:46 GMT

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