Rushton and genital size: one more time

J. Philippe Rushton asserts [1]:

Orientals are the most K, Blacks are the most r, and Whites fall in between. Being more r means: [. . .] more developed primary sexual characteristics (size of penis, vagina, testes, ovaries)

Rushton apparently has many convinced the above assertions are ironclad facts. They are not. Despite Rushton's sometimes selective presentation of evidence, what data exist (on "size of penis, vagina, testes") fail to consistently align with Rushton's Asian < White < African framework.

Penis size

Rushton claims [2]:

We averaged the ethnographic data on erect penis and found the means to approximate:
Orientals, 4 to 5.5 in. in length and 1.25 in. in diameter;
Caucasians, 5.5 to 6 in. in length and 1.5 in. in diameter;
blacks, 6.25 to 8 in. in length and 2 in. in diameter.

The numbers above are apparently lifted directly (or indirectly via Coon's Racial Adaptations) from a book by "A French Army Surgeon" ("Jacobus X" / Jacobus Sutor) published in 1898 (so much for "averages" of "the ethnographic data"; Rushton cites "A French Army Surgeon" as merely an "e.g." of "the ethnographic record", but Rushton's "ethnographic record" is apparently limited to the supposed observations of a single 19th-century individual).

The numbers given for blacks (ranging up to "8 in. in length" for population means) are implausible on their face, and no modern study of blacks comes close to supporting anything but the very low end of that suggested range.

A study of Nigerians (n=115) finds "mean [stretched] penile length was 13.37 cm [5.26 inches] with a median of 13 cm" [3]. Another study, on 320 Nigerians, finds "average [presumably flaccid] length of the penis (81.6 +/- 0.94 mm); circumference of the penis (88.3 +/- 0.02 mm)" [4].

The Kinsey data, which may be less than ideal but which are cited by Rushton both directly and indirectly, suggest any difference in mean penile dimensions between black and white men in America is measurable in fractions of an inch:

White males had an average flaccid penis length of 4.0 inches, whereas the average black male's detumescent member measured 4.3 inches. But when erect, the average white penis was 6.2 inches long, whereas the average black's was 6.3 inches--still longer, but not by much. (Average circumference for whites was 3.7 inches; for blacks, 3.8.)

When Rushton cites WHO condom standards in support of his theory, he is merely indirectly referencing the Kinsey data (plus a sample from Thailand, and one from Australia). WHO did no original research. Their sole "African" sample is the American black sample from Kinsey [7].

[Update: Rushton claims the WHO specify three condom sizes [1]:

The World Health Organization Guidelines specify a 49-mm-width condom for Asia, a 52-mm-width for North America and Europe, and a 53-mm-width for Africa.

I'd taken Rushton at his word here and had not bothered to check his WHO claim beyond determining that WHO did no original research on the subject (as stated above). In reality, it's clear from the guidelines that WHO specify exactly two widths [7]:

WHO specifies a width of 49 mm or 53 mm with a tolerance of ±2 for individual condoms and ±1 for the average of the lot.

The WHO don't make distinctions among Europe, Africa, and Asia, but between Asia and everyone else [7]:

Condoms are made in various widths. Based on studies in Australia, Thailand and the USA, and the experience of major agencies, the wider condoms (flat width 52-55 mm) will be preferred in Australia, Africa, Europe, Latin America, the Middle East and North America, and the narrower condoms (47-51 mm) will be preferred in several Asian countries (see Appendix III). Other widths are also made for small specialized markets.

Note: the ranges encompass tolerances in the specification; only two distinct widths are specified.]

Testes size

Rushton reviews most of the evidence of which I'm aware in his 1987 paper [2]:

Measurements taken from living subjects as well as those at autopsy, show the size of testes is twofold lower in Asian men than Europeans (9 g vs 21 g), a difference too large to be accounted for entirely in terms of body size (Diamond, 1986; Short, 1984). [. . .] Contrary to the general trend, Freeman (1934) observed that, at autopsy, American blacks had less heavy testes than American whites (13g vs 15g). [. . .] Subsequently Daniel, Fienstein, Howard-Peebles, and Baxley (1982) found no black-white difference in testicular volume among American adolescents, while Ajmani, Jain, and Saxena (1985) found larger scrotal circumference in Nigerians than Europeans (212.6 mm vs 195.1 mm or 8.37 in. vs 7.68 in.)

Strangely, by 2000, Rushton seems to have grown somewhat amnesiac [1]:

Race differences in testicle size have also been measured (Asians = 9 grams, Europeans = 21 g). This is not just because Europeans have a slightly larger body size. The difference is too large. A 1989 article in Nature, the leading British science magazine, said that the difference in testicle size could mean that Whites make two times as many sperm per day as do Orientals. So far, we have no information on the relative size of Blacks.

Rushton also conveniently ignores "A French Army Surgeon" where the latter's claim fails to line up with the former's theory:

In no branch of the human race are the male organs more developed than in the African Negro. I am speaking of the penis only and not of the testicles, which are often smaller than those of the majority of Europeans.

Vaginal size

Rushton claims (apparently again relying on "A French Army Surgeon"):

Women were proportionate to men, with Orientals having smaller vaginas and blacks larger ones, relative to Caucasians.

Modern studies fail to bear out this claim, which tends to further reduce the credibility of Rushton's 19th-century source. One study using MRI finds "[r]ace was not associated with any differences in measurements of vaginal dimensions" [5]. A different study finds [6]:

posterior cast length is significantly longer, anterior cast length is significantly shorter and cast width is significantly larger in Hispanics than in the other two groups and (2) the Caucasian introitus is significantly greater than that of the Afro-American subject.

Nor do the "Afro-American" subjects have deeper vaginas: "[a]verage rod lengths for Caucasians and Afro-Americans were 11.51 and 11.18 cm [. . .] significantly different as measured by t test" [6].

References

[1] Race, Evolution, and Behavior 2nd Special Abridged Edition (pdf)

[2] Rushton, J.P. & Bogaert, A.F. (1987) Race differences in sexual behavior: Testing an evolutionary hypothesis. Journal of Research in Personality 21(4): pp. 536-7 (link)

[3] Orakwe JC et al. Can physique and gluteal size predict penile length in adult Nigerian men? West Afr J Med. 2006 Jul-Sep;25(3):223-5. (link)

[4] Ajmani ML et al. Anthropometric study of male external genitalia of 320 healthy Nigerian adults. Anthropol Anz. 1985 Jun;43(2):179-86. (link)

[5] Barnhart KT et al. Baseline dimensions of the human vagina. Hum Reprod. 2006 Jun;21(6):1618-22. Epub 2006 Feb 14. (link)

[6] Pendergrass PB et al. Comparison of vaginal shapes in Afro-American, caucasian and hispanic women as seen with vinyl polysiloxane casting. Gynecol Obstet Invest. 2000;50(1):54-9. (link)

[7] WHO Global Programme on AIDS. Specification and Guidelines for Condom Procurement. Appendix VII, Regional or Ethnic Differences in Erect Penis Size. Geneva: WHO, 1995. (pdf)