By Scott A McGreal MSc.
Please note that this article contains sexually explicit discussion.
One of the more intriguing ideas to emerge out of evolutionary psychology is that a man’s interest in performing oral sex on a woman serves the purpose of testing whether a woman has recently been unfaithful. 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.
According to many evolutionary psychologists, men have been concerned with detecting and counteracting infidelity by their partners through human history. Many scholars have focused on the occurrence of sperm competitionwhich occurs when the sperm from two or more males occupy a woman’s reproductive tract at the same time, and hence compete to fertilise her ovum. Scholars have claimed that men have evolved certain mechanisms to deal with the threat of sperm competition (Pham & Shackelford, 2013). For example, some research has found that men ejaculate a greater volume of sperm when they have been separated from their partner for a good period of time compared to when they have been in each other’s company for the same amount of time. This is presumed to occur because there is a greater risk that the woman may have been unfaithful in her partner’s absence.
Pham and Schackelford (2013) 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 2006 book, but this study is the first to test this empirically. The idea is that oral sex may allow a man to detect the presence of another man’s semen through smell or taste. Pham and Schackelford’s study did not test whether men can actually detect semen in this manner (admittedly a difficult thing for a research study to test). What they did test were the hypotheses that men with more attractive partners (presumed to present a greater “recurrent risk of sperm competition”) would be more interested in performing oral sex, and that they would perform it for a longer duration “to better detect rival semen.” Contrary to what has been claimed elsewhere, the authors did not claim that men consciously perform oral sex because they think their partner has been unfaithful. 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.
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