Well, there are significant differences in testes size by race; penis length is more up in the
One can find the following information I reproduce in the book Sexual Selection and the Origin of Human
Mating Systems, the most current title on the subject, from a leading researcher in the field of primate sexual selection, a
certain Alan Dixson. The title of the book hints at the evolutionary reason why such differences
should be expected and are found: Wherever the mating systems of two closely related species,
populations, races, whatever, differ, there will be differences in the size of the male sexual
appartus due to male intrasexual selection. Natural selection operates more strongly in the species,
population, race, etc. whose males percentage-wise pass fewer of their genes into the next generation.
For example, chimpanzees, our closest cousins, have 3 times the size of testes humans do, adjusted
for body weight; in contrast to our relatively fidelitous long-term pair bonding, chimpanzees males
vie in multi-male multi-female coalitions to rise to the alpha position, where they hope to monopolize some
huge percentage of female matings by virtue of their position. Thus, more is stake for individual
chimpanzee males than for we lucky humans; to succeed evolutionarily, each one must make the best of each opportunity it is afforded, and thus natural selection has introduced innovations like large testes,
elaborate penis morphologies, and indeed strange things like post-copulatory plugs to further those ends.
Micro-differences between human populations arise from the same architecture: For example, because polygyny is
more common as one goes towards the equator, meaning fewer males in those areas being able to pass on their
genes, one might expect to find the signs of intensified intrasexual competition, such as larger
testes, longer penises, and larger canines, and one does in fact find those things.
Anyway, to the data. Dixson begins with testes size, and so shall we:
There are considerable differences in testes size and between human populations around the world.
These differences cannot be accounted for solely on the basis of variations in body weight (Short
1984; Diamond 1986.) [...] Although differences in body size may make some small contribution to the
ethnic variations in testes size ....it is much more likely that fundamental differepences in testes
size exist in different human populations.
OK, so what exactly are these differences? Dixson informs us:
Turning to measurements of combined testes size, there is a strong trend towards the occurence of
small testes in men from Asia (China, Japan, Korea, and perhaps in India) as compared to
measurements from European and African populations, or their ethnic derivatives. (e.g., in the USA
and Australia.) These differences are quite striking [...] smallest by far are the testes of 209
Hong Kong Chinese, weighed in two separate studies.
In the interleaving paragraphs, he goes on dryly about various summary statistics of the comparison,
which I'll leave for the reader to divine for themselves in the appending charts. Continuing, Dixon
An interesting comparison is provided by Ajmani, Jain, and Saxena's (1985) measurements of Nigerian
men. [...] Even if we allow for an overestimate of testicular volume in this study (due to a failure
to control for scrotal thickness, see Table 2.2.) Nigerian men have testes more than twice as large
as those of Hong Kong Chinese subjects of similar height [...] Next smallest are the testes of
Japanese men (averaging 30 ml and 35 ml in studies by Nakamura (1961) and Fujii et. al (1982)). The
same is true for studies of Korean men....by comparison, the weights or volumes of testes in men in
UK, France, Scandinavia, and other parts of Europe, as well in the USA, Australia, and Nigeria are
larger on average than for those men in Asian populations in which data exist...largest of all are
the testes of 209 Nigerian medical students (50.1 ml, Amjani et al. 1985) and three black African
Americans measured orginally by Schultz (50.2g).
Intriguing. Dixson goes on at length, with human-primate intercomparisons, which is actually the real thrust of the book. Later, though, it's on
to ethnic differences in penile length:
On average, the human penis is 15-16 cm long, and 10-12 cm in circumference, during tumescence. There
is considerable individual variability in penile size, however. [...] There may be ethnic
differences in penile dimensions, but these remain uncertain, due to lack of reliable comparative
data. Potts and Short refer to a survey (conducted by Japanese prostitutes) reporting a slightly
shorter average length of erection in Japanese males (13.75 cm) as compared to westerners. Rushton
and Bogaert (1987) cite Nobile (1982) who used the Kinsey data to examine possible differences in
size between American Blacks and Caucasians...[they] emphasize that the length of the flaccid and
erect penis is significantly larger in black males than in Caucasians. However, none of the
differences they cite exceed 0.5 in., and thus one wonders whether the methods used by Kinsey et. al
might have produced differences to subjective bias [...]
The only other study I was able to locate...recorded that Nigerian medical students had penes
averaging 8.16cm in length and 8.83 cm when flaccid...Kinsey['s] measurements for American
Caucasians [are] as follows: length 9.65 cm, and circumference, 7.9 cm. As matters stand, therefore,
it would not be justifiable to conclude that robust ethnic differences in penile size have been
demonstrated in human populations.
In other words, the study conducted directly in Africa found shorter average penis lengths than
Kinsey found, though Kinsey found the stereotyped hierarchy within his own data. However, there's an obvious paucity of data due to the sensitivity of the subject, so there is not enough to conclude that there's a significant difference.
Now, all that's left are the various charts to peruse for amusement. Do note that in the final
chart, inter-race differences between humans are larger than between species orangutan-gorilla
differences, belying all sorts of common mythology about race: