The Good Jeans Hypothesis
Just about every article I read on women’s preferences for sexual dimorphism in men points out that the data are consistent with the good genes hypothesis. There are a couple of technical variations of this hypothesis, but they all are based on the reasonably well-established connection between testosterone and impeded immune system functioning. The idea is: testosterone interferes with immunity so males who display increased phenotypic influences of testosterone must have better genes, in order to combat the toxic effects of the hormone on the immune system. So far, so good. The hypothesis is perfectly reasonable: however, it is far from substantiated. A central issue for me involves the notion of trade-offs: it is possible that the larger muscles and increased status-seeking that are associated with testosterone might result in higher status which could produce adaptive benefits, e.g., increased access to food which, at least theoretically, could compensate for the correlated decrease in immune functioning. I am not arguing that this has been shown – but I am emphasizing the hypothetical nature of the good genes hypothesis.
Regardless of the veracity of the good genes hypothesis, the beauty literature is lacking in proximal explanations for women’s increased interest (during ovulation) in sexually dimorphic features in men. Broadly speaking, the evidence continues to build that women find moderately increased levels of sexual dimorphism in males more attractive during fertile periods than during non-fertile periods (e.g., Johnston et.al, 2001). The question is, why?
My hypothesis is that ovulating women have higher levels of libido (to use the vernacular, they are a little hornier) and, when hornier, are more likely to prefer males who look like virile, competent, enthusiastic – good – lovers. Evidence is accruing that women have increased interest in sex during/around ovulation (e.g., Wilcox, et.al. 2004; Tarin & Gomez-Piquer, 2002). I also believe there is some evidence to support the assertion that the increased attraction to sexually dimorphic characteristics around ovulation could be due to the belief that such features signal competence as a lover rather than an attraction to increased masculinity per se.
Using frame numbers in the quick time movie (the format the morphed faces were presented in): the average attractive male face was depicted in frame 284 (below middle). When peri-ovulatory, women found frame 245 (below right) the most attractive.
This shift in preference is a shift toward both increased sexual dimorphism and to the perception of increased competence as a lover. Since the average optimally attractive male face (frame 245) more closely approximates the face that looks like the optimal lover (approximately: frame 190) rather than the one identified as masculine (frame 115), it seems prudent to consider the possibility that peri-ovulatory shifts in attractiveness ratings might result from an increased interest in the perceived sexual characteristics of the depicted male rather than in his masculinity per se.
Blue Jeans photo courtesy of Hendrike, 2005. Wikipedia Commons.
Johnston, V. (2001). Male facial attractiveness: evidence for hormone-mediated adaptive design Evolution and Human Behavior, 22 (4), 251-267 DOI: 10.1016/S1090-5138(01)00066-6
Tarin, J. (2002). Do women have a hidden heat period? Human Reproduction, 17 (9), 2243-2248 DOI: 10.1093/humrep/17.9.2243
Wilcox, A. (2004). On the frequency of intercourse around ovulation: evidence for biological influences Human Reproduction, 19 (7), 1539-1543 DOI: 10.1093/humrep/deh305