Support for Testosterone Theory of Human Evolution

James Howard (
Fri, 30 Aug 1996 20:06:00 GMT

I just found this citation that supports my theory that hominid
migration was forced. That is, it shows, in a free-living primate,
that individuals of lower testosterone are forced away from the
breeding group.

James Howard
(read my theory at on the web)

Wickings EJ, et al. "Testicular Function, Secondary Sexual
Development, and Social Status in Male
Mandrills (Mandrillus sphinx)" Physiology & Behavior 1992; 52: 909

"Positive correlations between dominance rank and plasma testosterone
levels have been described for adult males of several primate species
in captivity, but the relevance of such observations to free-ranging
animals is unclear. CIRMF in Gabon maintains a breeding group of 45
mandrills in a six hectare, naturally rainforested enclosure. This
study describes correlations between dominance rank (in agonistic
encounters), levels of plasma testosterone, testicular volume, body
weight, and development of secondary sexual characteristics (red and
blue sexual skin on the muzzle and rump areas) in male mandrills under
semifree ranging conditions. Two morphological and social variants of
adult male mandrill were identified. Large-rumped or fatted adult
males (n = 3) remained in the social group and exhibited maximal
development of sexual skin coloration as well as large testicular size
and highest plasma testosterone levels. By contrast, slimmer-rumped or
nonfatted males (n = 3) lived a peripheral or solitary existence and
these exhibited less development of their secondary sexual coloration
and had smaller testes and lower plasma testosterone levels.
Longitudinal studies of gonadal development in these six males
revealed that testicular volumes and plasma testosterone levels
increasedmost rapidly during pubertal development (4-5 years of age)
in the three animals which proceeded to the fatted condition.
These included the highest ranking, group-associated male which
exhibited the most intense sexual skin coloration and had higher
testosterone levels, although this was not correlated with testicular
volume. This study shows that in the male mandrill social factors and
reproductive development are interrelated."