A recently published study aimed to test this theory and found that men who are in long term relationships with more attractive women are more interested in performing cunnilingus on their partners. The authors argued that more attractive women are more likely to be targeted by other men who might try to lure them away from the relationship. They concluded that their results confirm their hypothesis that oral sex functions to detect infidelity. Although interesting, their results are inconclusive because they did not appear to consider a more obvious explanation for their findings.
Image courtesy of imagerymajestic at FreeDigitalPhotos. Pham and Schackelford argued that men with more attractive partners are at a greater recurrent risk of sperm competition because other men are more likely to woo them into having affairs.
Therefore, men with more attractive partners have more reason to be concerned about and more likely to engage in behaviour aimed to detect infidelity.
The idea that cunnilingus, oral sex performed on a woman, could function to detect infidelity was proposed in a book, but this study is the first to test this empirically. It is possible for a behaviour to serve an evolutionary function without a person knowing what that function is. They simply need to want to do it, even if they do not know why. This is a gross misrepresentation of what evolutionary psychology is about and in fairness to the authors of the study they were attempting to actually test whether or not their hypothesis about the adaptive function of oral sex is valid, rather than just assuming it is.
It is quite possible that oral sex has no evolutionary function in itself. Humans are a highly sexed species compared to most mammals Diamond, and engage in many non-procreative sexual acts, perhaps for pleasure alone.
Oral sex might simply be a by-product of this interest in sex that humans have. However, if it can be shown that this particular behaviour appears to serve a definite purpose that has an evolutionary history, a reasonable case can be made that it has an adaptive function.
To test their hypotheses, the authors recruited heterosexual males in committed relationships that had lasted at least one year. These were asked a series of questions about how attractive they thought their partners were to themselves and to other men ; about their relationship satisfaction; and their most recent sexual experience.
I thought the wording of these questions was somewhat peculiar. Recurrent risk and duration of intercourse each predicted duration of oral sex independently of relationship length and relationship satisfaction. This indicates that the more attractive a man found his partner, the more interested he was in performing oral sex, and the longer he performed it for.
The authors took this as evidence in support of their hypothesis that oral sex functions to detect infidelity when recurrent risk of sperm competition is high. Strangely, they did not appear to consider the more obvious explanation that the more attractive a man considers his partner, the more interested he would be in performing sex acts in general with her.
That is, greater attraction would produce greater sexual excitement generally, and hence greater willingness to engage in a variety of sexual acts. Additionally, reciprocity may play a role.
That is, men might perform oral sex with the expectation of receiving it in return. To their credit, the authors do consider some alternative explanations of their findings that could be considered in future studies. Research has found that women are more sexually satisfied the more frequently they receive oral sex. Other research has found that the more sexually satisfied a woman is, the less likely she is to be unfaithful. Female sexual satisfaction was not assessed in this study, and the authors acknowledge that future research should consider whether the relationship between attractiveness and male interest in oral sex remains after taking into account desire to satisfy the partner.
This seems to me like a very reasonable alternative explanation. The other alternative they considered, which I consider to be much more speculative, is based on the idea that a woman retains more sperm in her uterus when she has an orgasm.
This idea is based on a study by Baker and Bellis which actually claimed to have found that female orgasm increased sperm retention only when it occurred between one minute before and 45 minutes after ejaculation.
Orgasm occurring more than one minute before ejaculation had no effect on sperm retention according to this study. If Baker and Bellis are correct performing oral sex would not be effective in increasing sperm retention unless the timing was very specific.
Image courtesy of photostock at FreeDigitalPhotos. Some of these alternative explanations, such as those involving female satisfaction, and my own hypothesis that female attractiveness generally increases male interest in sexual activity seem like more obvious explanations. This does not necessarily mean that the authors are incorrect, only that more research is needed to test these different explanations.
For example, studies might assess whether men with more attractive partners are also more interested in other activities associated with sexual foreplay, such as kissing and so on.
It would then be possible to test whether interest in oral sex is independent of interest in these other activities. It is also possible that oral sex might serve a combination of functions and that all of these hypotheses have a grain of truth. For example, if the function of cunnilingus was to detect whether a woman had been sexually active with another male, it would seem reasonable that if she had in fact been unfaithful she might try to avoid receiving cunnilingus to avoid detection.
While it may be true that men are more likely to target attractive women for affairs, it is also the case that the woman actually has a say in the matter. Some women are more likely to be unfaithful than others and this may be related to her character and choices as much as her looks.
Please do not reproduce without permission. Brief excerpts may be quoted as long as a link to the original article is provided. See this article by Tooby and Cosmides, leading figures in the field, which shows how Gould completely misrepresented their work, in which they explicitly stated that most human behaviours are probably by-products without an evolutionary function.
The findings by Baker and Bellis do not appear to have been replicated so their claims might be taken with a grain of salt. Other posts discussing sexuality and evolutionary psychology.