There are many factors that determine an individual's appeal on the mating market, and not surprisingly some of these are sex-specific. For example, height and social status carry greater import in establishing a man's desirability whereas youth and beauty are much more crucial when it comes to a woman's mating allure. Note though that the variance in mating success is much greater for men than women. For example, highly desirable men might have sexual access to a large number of women while others twiddle their thumbs in sexual frustration. On the other hand, women's mating success does not vary much. In other words, the difference in mating success between the most and least desirable women on the mating market is much lesser than the corresponding difference for men.

From a strictly biological/genetic perspective, reproductive fitness is the ultimate measure for quantifying one's mating success (i.e., success in passing one's genes to subsequent generations, which is oftentimes measured via the number of offspring that an organism has over its lifetime). This brings me to the topic of today's post, namely given that mating success is measured over the entire reproductive lifetime of an individual, what are some factors that determine the number of sexual partners that an individual might have over his/her lifetime? Of course, from a gene propagation perspective, the number of lifetime sexual partners carries greater implications for men's reproductive interests than they do for women's.

In a paper recently published in Hormones and Behavior, Thomas V. Pollet, Leander van der Meij, Kelly D. Cobey, and Abraham P. Buunk explored the relationship between individuals' levels of circulating testosterone (T; collected via salivary assays) and the self-reported number of lifetime (opposite sex) sexual partners. They utilized a very large data set (the National Social Life, Health, and Aging Project), which consists of individuals whose ages vary between 57 and 85 (n = 3,005). As Pollet et al. explained, the postulated link could be due to one of two reasons: (1) Individuals (especially males) who possess higher T levels are likely to be more motivated to pursue multiple mating opportunities (T is associated with libidinal drive). (2) Individuals (especially males) who possess higher T might be deemed more attractive on the mating market and hence might garner more reproductive opportunities. Pollet et al. also collected data on several possible covariates including educational attainment, body mass index, ethnicity, age, time at which the salivary samples were taken, and medication that might affect the T readings.

Here are the key findings (as relating to the specific issues raised in this post; all samples were at least 700+ in size): the correlation between T and number of lifetime sexual partners was highly significant for men (p = 0.0002) and this effect remained highly significant (p = 0.0009) even when taken into account the possible effects of the covariates. For women, the correlation was marginally significant (p = 0.088) but became statistically significant (p = 0.026) when the covariates were partialled. Bottom line: The postulated link between circulating T levels and number of lifetime sexual partners was much stronger for men.

Readers interested in the effects of testosterone across numerous other settings might wish to check out some of my earlier posts including T levels at a sex club (here), the effects of conspicuous consumption (driving a Porsche) on men's T levels (here), the effects of a woman's "fertile" smell on men's T levels (here), spectators' T levels at a World Cup final (here), men's voices and their T levels (here, here, and here), and the digit ratio as a proxy measure of in utero exposure to T and its relationship to consumption (here).

Finally, the teaser image speaks to the investigated link in the following way: Casanova was a voracious womanizer. Did he have high T levels? Whereas his circulating T levels were never measured (!), his ring finger was reputed to be exceptionally long (as reported in John Manning's book The Finger Ratio). In other words, Casanova's digit ratio was highly masculinized (via exposure to T in utero).

Source for Image:

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