Ryan, C. and C. Jetha. 2011. Sex at Dawn: How We Mate, Why We Stray, and What It Means for Modern Relationships. New York, USA: Harper Perennial.
As a way of testing this hypothesis, we should find that relative penis and testicle data differ among racial and cultural groups. These differences—theoretically due to significant and consistent differences in the intensity of sperm competition in recent historical times—are what we do find, if we dare to look.
Because fit is so important in the effectiveness of condoms, World Health Organization guidelines specify different sizes for various parts of the world: a 49-millimeter-width condom for Asia, a 52-millimeter width for North America and Europe, and a 53-millimeter width for Africa (all condoms are longer than most men will ever need). The condoms manufactured in China for their domestic market are 49 millimeters wide. According to a study conducted by the Indian Council of Medical Research, high levels of slippage and failure are due to a bad fit between many Indian men and the international standards used in condom manufacture.
According to an article published in Nature, Japanese and Chinese men’s testicles tend to be smaller than those of Caucasian men, on average. The authors of the study concluded that “differences in body size make only a slight contribution to these values.” Other researchers have confirmed these general trends, finding average combined testes weights of 24 grams for Asians, 29 to 33 grams for Caucasians, and 50 grams for Africans. Researchers found “marked differences in testis size among human races. Even controlling for age differences among samples, adult male Danes have testes that are more than twice the size of their Chinese equivalents, for example.” This range is far beyond what average racial differences in body size would predict. Various estimates conclude that Caucasians produce about twice the number of spermatozoa per day than do Chinese (185–235 × 106 compared with 84 × 106).
These are dangerous waters we’re swimming in, dear reader, suggesting that culture, environment, and behavior can be reflected in anatomy—genital anatomy, at that. But any serious biologist or physician knows there are anatomical differences expressed racially. Despite the hair-trigger sensitivity of these issues, not to consider racial background in the diagnosis and treatment of disease would be unethical.