Development of agriculture in modern Blacks also seems to have led to high testosterone levels. Groups with the highest testosterone in the world today are primitive agriculturalists.
Hunter-gatherers tend to have lower testosterone. This is because in hunter-gatherer society, women need men to survive. So they grab one pretty quickly and get married.
In primitive agricultural societies, women do not need men, since they can farm on their own. So they can afford to be choosy. These societies have tended to develop in a polygynous way, where a few high-ranking males monopolize most of the females, and the rest of the men get few or none.
Sub-Saharan Blacks are highly polygynous, and this resulted in intense competition for fewer women and selection for very robust male body types. SS Blacks are more robust than Whites on all variables. In Namibia, the polygynous Kavango have much higher testosterone than the much less polygynous !Kung.
Broadly speaking, lifetime exposure to testosterone is reflected in the incidence of prostate cancer, with the world’s highest incidences being among African-American men (Brawley & Kramer, 1996). It was once thought that lower incidences prevail among Black West Indians and sub-Saharan Africans, but this apparent exception is now ascribed to underreporting (Glover et al., 1998; Ogunbiyi & Shittu, 1999; Osegbe, 1997).
This picture has been confirmed by a recent American study:
From the 1970’s to the current statistical analysis of the National Cancer Institute Surveillance, Epidemiology, and End Results program African-American men have continued to have a significant higher incidence and mortality rate than European-American men. Autopsy studies show a similar prevalence of early small subclinical prostate cancers but a higher prevalence of high grade prostatic intraepithelial neoplasia.
Clinical studies show a similarity in prostate cancer outcome when pathological stage is organ confined but a worse outcome when disease is locally advanced and metastatic in African-American vs European-American men. There is increasing genetic evidence that suggest that prostate cancer in African-American vs European-American men may be more aggressive, especially in young men.
It was also confirmed by a recent British study (prostate cancer rates are somewhat lower in Black British men because a higher proportion of them have one White parent):
Black men in the United Kingdom have substantially greater risk of developing prostate cancer compared with White men, although this risk is lower than that of Black men in the United States. The similar rates in Black Caribbean and Black African men suggest a common genetic etiology, although migration may be associated with an increased risk attributable to a gene–environment interaction” (Ben-Shlomo et al 2008).
We are only just beginning to identify the actual genes that account for the White/Black difference in prostate cancer risk. The most recent study was Benson 2014.
The 2:1 black-to-white ratio in prostate cancer rates is already apparent at age 45 years, the age at which the earliest prostate cancer cases occur.
This finding suggests that the factor(s) responsible for the difference in rates occurs, or first occurs, early in life. Black males are exposed to higher testosterone levels from the very start.
In a study of women in early pregnancy, Ross found that testosterone levels were 50% higher in Black women than in White women (MacIntosh 1997). Ross speculates that exposure to such high levels in utero might reset the “gonadostat feedback loop” which regulates testosterone secretion to a higher level. According to Ross, his findings are “very consistent with the role of androgens in prostate carcinogenesis and in explaining the racial/ethnic variations in risk” (MacIntosh 1997).
Testosterone has been hypothesized to play a role in the etiology of prostate cancer, because testosterone and its metabolite, dihydrotestosterone, are the principal trophic hormones that regulate growth and function of epithelial prostate tissue.
Many studies have shown that young Black men have higher testosterone than young White men (Ellis & Nyborg 1992; Ross et al. 1992; Tsai et al. 2006).
With respect to the Black/White difference in testosterone level, African Americans have a clear testosterone advantage over Euro-Americans only from puberty to about 24 years of age (Abdelrahaman et al., 2005; Ross et al., 1986; Winters et al., 2001). This advantage then shrinks and eventually disappears at some point during the 30s (Gapstur et al., 2002). The pattern then seems to reverse at older ages. In later years, White men have higher testosterone than Black men (Nyborg, 1994, p. 111-113).
This makes it very difficult if not impossible to explain differing behavioral variables, including higher rates of crime and aggression, in Black males over the age of 33 on the basis of elevated testosterone levels.
Critics say that more recent studies done since the early 2000’s have shown no differences between Black and White testosterone levels. Perhaps they are referring to recent studies that show lower testosterone levels in adult Blacks than in adult Whites. This was the conclusion of one recent study (Alvergne et al. 2009) which found lower T levels in Senegalese men than in Western men. But these Senegalese men were 38.3 years old on average.
These critics may also be referring to various studies by Sabine Rohrmann which show no significance difference in T levels between Black and White Americans. Age is poorly controlled for in her studies.
More seriously however, she used serum samples that the National Center for Health Statistics had earlier collected as part of its Third National Health and Nutrition Examination Survey (NHANES III). Only 1,479 samples were still available out of an initial total of 1,998, i.e., one quarter were missing. An earlier study had used the same serum bank for research on a sexually transmitted disease: Herpes Simplex virus type 2 (HSV-2).
That study found that more than 25% of the samples for adults between 30 and 39 years were positive for HSV-2. It is likely that those positive samples had been set aside, thus depleting the serum bank of male donors who were not only more polygamous but also more likely to have high T levels. This sample bias was probably worse for African American participants than for Euro-American participants.
Young Black males have higher levels of active testosterone than European and Asian males. Asian levels are about the same as Whites, but a study in Japan with young Japanese men suggested that the Japanese had lower activity of 5-alpha reductase than did U.S. Whites and Blacks (Ross et al 1992). This enzyme metabolizes testosterone into dihydrotestosterone, or DHT, which is at least eight to 10 times more potent than testosterone. So effectively, Asians have the lower testosterone levels than Blacks and Whites. In addition, androgen receptor sensitivity is highest in Black men, intermediate in Whites and lowest in Asians.
Let us look at one study (Ross et al 1986) to see what the findings of a typical study looking for testosterone differences between races shows us. This study gives the results of assays of circulating steroid hormone levels in white and black college students in Los Angeles, CA. Mean testosterone levels in Blacks were 19% higher than in Whites, and free testosterone levels were 21% higher. Both these differences were statistically significant.
Adjustment by analysis of covariance for time of sampling, age, weight, alcohol use, cigarette smoking, and use of prescription drugs somewhat reduced the differences. After these adjustments were made, Blacks had a 15% higher testosterone level and a 13% higher free testosterone level. A 15% difference in circulating testosterone levels could readily explain a twofold difference in prostate cancer risk.
Higher testosterone levels are linked to violent behavior.
James Dabbs, Jr., studied 4,462 men in 1990 and found that “the overall picture among the high-testosterone men is one of delinquency, substance abuse and a tendency toward excess.” These men, he added, “have more trouble with people like teachers while they are growing up, have more sexual partners, are more likely to have gone AWOL in the service and to have used hard drugs,” particularly if they had poor educations and low incomes.
A separate study by Dabbs of young male prison inmates found that high testosterone levels were associated with more violent crimes, parole board decisions against release, and more prison rule violations. Even in women, Dabbs found, high testosterone levels were related to crimes of unprovoked violence, increased numbers of prior charges, and decisions against parole.
The latest study by Dabbs et al., which pooled data from two groups of prisoners, measured testosterone levels in the saliva of 692 adult male prisoners. The researchers found that inmates who committed crimes of sex and violence had higher testosterone levels than inmates who were incarcerated for property crimes or drug abuse. In addition, they say, “inmates with higher testosterone levels… violated more rules in prison, especially rules involving overt confrontation.”
Studies suggest that high testosterone lowers IQ (Ostatnikova et al 2007). Other findings suggest that increased androgen receptor sensitivity and higher sperm counts (markers for increased testosterone) are negatively correlated with intelligence when measured by speed of neuronal transmission and hence general intelligence (g) in a trade-off fashion (Manning 2007).
Black females have higher IQ’s than Black males. Black female IQ is 2.4 points higher than Black male IQ. There are twice as many Black females as males with IQ’s over 120 and five times as many females as males with IQ’s over 140.
Acknowledgements: I would like to thank Dr. Peter Frost for his invaluable help in writing this paper.
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