The spandrels of Santa Barbara? A new perspective on the peri-ovulation paradigm

Abstract

Numerous recent studies document peri-ovulatory increases in women's physical attractiveness and in their preferences for certain male traits, which appear to be linked to cyclical fluctuation in levels of ovarian hormones. Changes in physical traits are subtle, leading to the widespread conclusion that cues of ovulation are adaptively concealed. It has been argued that concealment enables women to pursue a mixed-mating strategy characterized by pair-bonding with opportunistic extra-pair copulation with high quality mates when conception is possible. Men's preferences for peri-ovulatory cues and women's cyclical preference shifts are thus also argued to reflect distinct psychological adaptations. Here, we re-interpret the evidence for each of these putative adaptations and argue that cyclic changes need not result from incomplete concealment of ovulatory status. We also emphasize that ovarian hormone levels underpin between-individual differences in both women's attractiveness and their mate preferences, which influence the sexes' mate choice decisions. We contrast the salience and efficiency of these within-and between-individual effects, and suggest that, while both effects have the potential to influence mating behavior, the between-individual effects are stronger and more robust. This introduces the possibility that both men's increased attraction towards peri-ovulatory women and women's cyclical shifts in preference for certain male traits may not constitute adaptations per se, but are, instead, inevitable byproducts, or 'perceptual spandrels', of putative adaptations related to between-individual differences in reproductive potential. Our framework parsimoniously explains several observable phenomena, and potentially could transform the way evolutionary researchers interpret changes in behavior associated with the menstrual cycle.

Human mating strategies: from past causes to present consequences

“…Cyclic hormone fluctuations also calibrate both women's sexual desire and behavior. For example, estradiol and progesterone show positive and negative effects, respectively, on self‐reported sexual desire, women appear to wear clothing to attract men during the ovulatory phase, and their likelihood of wearing red at this time (another proposed courtship tactic) increases in line with the estradiol‐to‐progesterone ratio (although—as noted by Havlíček et al—this is at odds with the idea of concealed ovulation; see Box ).…”

“…First, it has been pointed out that the idea that women attempt to signal their ovulatory status (e.g., by wearing more revealing or sexier clothing at ovulation 10 ) is at odds with the concept of functional advantages in concealing it. 11 Second, recent studies in which people rate stimuli of women collected during fertile and nonfertile phases of the menstrual cycle show that men (and women) can in fact discriminate some cues of estrus, [12][13][14] raising questions about how completely ovulation can be considered to be 'concealed.' Third, relatively inconspicuous ovulation is not exclusive to humans, being also observed in other primate species.…”

“…16 Fourth, in line with this suggestion, the relative inconspicuousness of ovulatory changes in women coupled with the low rate of ovulation detection in men has led some researchers to argue that these might plausibly be interpreted as simple nonadaptive by-products of underlying hormonal changes across the cycle. 11 In other words, both the argument that concealed ovulation is a specific adaptation and consequent conjecture regarding adaptive functional explanations, such as through enhancing paternity confidence, are rendered unnecessary. Finally, it should also be noted that the supposed outcome of the proposed adaptation, exclusive monogamy, is not the only mating pattern adopted across human populations and cultures.…”

Can women detect cues to ovulation in other women's faces?

“…Women were shown pairs of faces, one of which depicted an ovulatory face, the other a luteal face, and were asked to choose the more attractive woman. According to some authors ([8], see also [15]), facial signals of ovulation might be identical to what is typically seen as attractive in women's faces. If this were true we would expect that both women and men should find female faces showing ovulation cues more attractive.…”

Spandrels and trait delimitation: No such thing as “architectural constraint”

“…Proposed in 1979 by Gould and Lewontin, the metaphor evokes the four massive triangles that on vast piers subtend the central dome of Venice's Basilica of San Marco. These triangles are lavishly decorated with mosaics, and the argument goes that they are so appropriate to the artist's composition that a viewer might easily think that the triangles were deliberately placed for creating harmony (Fodor & Piattelli-Palmarini, 2011;Havliček, Cobey, Barrett, Klapilová, & Roberts, 2015;Houston, 2009). The message of the spandrels metaphor is that the four triangles were not, despite all appearances, placed for bearing decorations, but are instead an example of "architectural constraint," the inevitable consequence of making a round dome fit onto a square base (Brigandt, 2015;Fitch, 2012;Raff, 2012).…”