People often wonder: “Why do older men like younger women?” From the lay public to the psychologists, it’s an enduring question. The other day I stumbled upon an article over at the Huffington Post about younger women dating older men. The author gives the usual statistics regarding older men dating and marring younger women. Towards the end she quotes Lynn Philips, a psychologist and professor of Communication at the University of Massachusetts:

Philips argued that individual needy girls and exploitative men are not the only factors driving these relationships. “From music videos, to porn, to Disney, this all sits within this bigger cultural context of media images and cultural messages that absolutely eroticize and hyper-sexualize teen girls,” she said. “As much as we say we’re appalled by [these relationships] and concerned by them, there are things out there in the culture that make this happen.”

Philip points to American culture where TV and movie screens as well as online and print publications feature scores of young beautiful women to explain why older men go after younger women. This doesn’t seem totally unreasonable – beautiful women do dominate our visual and mental experiences throughout the day – and I’ve heard this argument before. This article, for example, argues that, “men’s sexual desire is driven by culture, not evolution.”

In his latest book Sex, Murder, and The Meaning of LIfe, Douglas Kenrick, whose research I mentioned a few posts ago, thinks otherwise. He believes that there is a “universal attraction between older men and younger women” to suggest that culture is actually the effect and not the cause. Here is an exert from a paper by Andrew Delton, Theresa Robertson and Douglas Kenrick done a few years back that summarizes this point with concrete data (I’ve included links to as many papers I could track down if anyone is interested).

Across 37 different cultures, Buss (1989) found that, on average, males preferred a mate who was about two and a half years younger. Buss also found that actual ages at marriage closely paralleled the stated male preference. Several studies by other evolutionary psychologists have suggested that this average discrepancy can be a bit misleading as a description of age preferences for people who are older than 30, or younger than 20 (Essock, 1989; Kenrick, Gabrielidis, Keefe, and Cornelius, 1996; Kenrick and Keefe, 1992; Otta, Queiroz, Campos, daSilva, Silveira, 1999; Wiederman and Allgeier, 1992). Using a variety of sources—singles ads and marriage statistics from cross-national and cross-generational samples—Kenrick and Keefe (1992) found that men in their 20s preferred or married women of roughly their own age, but as men aged they preferred or married women who were progressively younger than themselves. For instance, men in their 60s on the island of Poro (data were from the years 1913 to 1939) married women who were about 20 years younger. Although older men do prefer younger women, not all men seek out and/or marry women in their 20s. Kenrick and Keefe expected this based on a number of factors, including the countervailing preference for similarity, as well as the constraints of mutual choice (there is generally little to be gained by seeking a marital partner who is not likely to reciprocate your interest, and elderly men, regardless of their own preferences, may not be able to attract young attractive females). To further test the hypothesis that men prefer fertility rather than relative youth per se, Kenrick and colleagues (1996) interviewed adolescent males about who they would find attractive as a dating partner. These adolescent males indicated that females older than themselves—women in their early 20s—would be maximally desirable, although they also expressed awareness that those women would not likely reciprocate their interest. For males at this age, it is relatively older women who are maximally fertile. Men thus do not seem to be following a cultural rule that dictates “mate with a younger woman.” Instead, based on these studies and others, evolutionary psychologists concluded that males prefer young women as mates because, at most points in a male’s life, relative youth is a cue to fertility. (italics mine)

The evidence is clear: biology explains why older men are attracted to young women – not culture norms.

Here’s what I find interesting. Kenrick argues that in light of our evolutionary motives many consumer purchases could be considered “deeply rational”. Take a $400,000 Porsche. This car is a waste of money by any metric. It has little cargo space, a poor safety record, there are only two seats, poor gas mileage, etc. However, some people (mostly old rich men) buy it. While most economists would label this as an example of “irrational behavior”, Kenrick thinks otherwise:

Besides the decision-making variations arising from a person’s sex and life history stage, our model suggests that each individual decision-maker has several different economic subselves, and that the subself in charge right now depends on which adaptive threats and opportunities are currently prominent in the environment. What looks like irrationality to one subself may be deeply rational to another. Your marketplace subself, which is dominated by the question: “What’s in it for moi?” would be aghast at the exorbitant bill your parental subself has run up sending junior through college, for example. The logic of Deep Rationality suggests that fundamental biological motives such as mating and self protection should drastically change all the traditional behavioral economic biases, such as temporal discounting (the tendency to take a loss for an immediate payoff rather than wait for a larger one), and probability discounting (the tendency to prefer a certain payoff over a chance at a larger one). The same motives should also move around what a person regards as a luxury versus as a necessity, and should do so very differently for men and women. A series of experiments by Norm Li and his colleagues has already begun to demonstrate the profound importance of distinguishing between luxuries and necessities in different aspects of social decision-making.

In short, on the evolutionary level, it is rational to buy that Porsche because it is man’s natural way of advertising himself – if he wants to ensue that his genes get passed on to the next generation, it doesn’t seem all that stupid. Now, does this mean it is wise or right for a man to spend hundreds of thousands on that new car? Not at all, the naturalistic fallacy reminds us that something is not necessarily right just because it is natural. But Kenrick’s point helps us better understand why he would. Moreover, he reminds us that “on the evolutionary view, what seems irrational at the surface level may be, on closer examination, deeply rational.” So heads up Adam Smith, your standards for rational behavior aren’t the only ones.