Support for Testosterone Theory of Human Evolution

James Howard phis at sprynet.com
Mon Nov 11 06:05:14 EST 1996


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 http://naples.net/~nfn03605/ 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."





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