Before we begin, one thing to get out of the way: There are many people, both academics and non-academics, who think evolutionary psychology is utterly bogus.
Critics argue that evolutionary psychologists reinforce outdated gender assumptions and repackage modern cultural issues as "science." The discipline is not helped by infamous studies such as 2007's Biological components of sex differences in color preference, which suggested that girls like pink because their cavewomen forebears would have foraged for wild berries.
That said, proponents of evolutionary psychology argue that they draw their conclusions from the widest pools of human behavior, from patterns and trends discernible in cultures across the world. Which brings us to a recent study from this field of research.
A 2016 research paper from the University of Texas argues that women have affairs as a way of testing for superior partners. The so-called "mate-switching hypothesis," argues professor David Buss, can be used to explain the behavior of childless women, who tend to find it easier to switch mates.
"Over human evolutionary history, bad things could happen to a woman's existing long-term mate. He could become injured, diseased, killed, or decline in mate value." As a result, Buss argues, women evolved to cultivate back-up mates.
"If the regular partner started failing to provide the benefits inherent to the mate choice, or even inflicting costs, then the woman could trade up to a clearly better partner." In essence, prehistoric women traded in their previously diligent mates for better versions when they became sickly berry-hoggers who couldn't hunter-gather to save their lives.
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In Buss' view, the mate-switching theory explains why women have affairs—something that a competing evolutionary psychology approach, the good genes hypothesis, can't do. The good genes hypothesis argues that women will choose a potential mate whose offspring will have the best chance of survival. "The theory can't explain why women tend to become involved with their affair partners. If they were just after their good genes, they'd want short-term sex with no emotional involvement."
At the crux of Buss' argument is evidence that suggests that 79 percent of women fall in love with their affair partners, according to a 1985 study from Glass & White. "Men are much more motivated by sexual considerations in affairs and are less likely to fall in love with their affair partners. Whereas women tend to have affairs in order to cultivate back-up males."
I ask whether many women aren't just culturally conditioned to expect intimacy from sexual relationships—and hence, are more likely to develop feelings for their partners. "I don't make the distinction between our evolved and social psychology. What's at stake here is the nature of our evolved psychology." Buss goes on to argue that there's evidence that supports the view that men are generally better able to disassociate sex from emotional involvement. "It's universal. You go to South Africa or Australia or Botswana and you find the same thing."
Buss argues that women are constantly monitoring the "mate value" of their partner at all times. "My hunch is that people have these low-level assessment mechanisms going on all the time. So they meet someone new and question whether they, as an alternative, would be more attractive than their existing partner." In his research paper, Buss cites how inadequate economic support from the husband is often cited as a reason for divorce.
I ask whether the same principles apply to women with children. Buss argues that women with children are less likely to mate-switch to a superior mate. His brutal explanation for this is that, "in the mating market, having a kid with another man is a cost, not a benefit. It reduces your mate value."
Whether you agree with his findings or not—after all, many financially independent women choose to have affairs for no reason other than some fun, no-strings sex—Buss believes the area is fertile ground for further investigation.
"Somehow in the West we've come to evaluate relationships exclusively by the metric of how long they last," he says. "That's a mistake from an evolutionary perspective. There are a ton of potential new avenues for research."