Are men shaped by evolution to be more inclined toward casual sex? Or is it simply a function of how people are socialized? This recent variant of psychology’s (in)famous nature-nurture debate is the topic of an Op Ed piece in today’s NY Times. In the article, Darwin Was Wrong about Dating, the author Dan Slater notes that evolutionary psychologists have been developing Darwinian frames explaining why women are the choosier sex for the past forty years. Except now, he writes, “over the past decade, sociocultural explanations have gained steam”. He goes on to cite several studies where the findings suggest maybe much of the gender differences in sexual behavior are contextually based. From this he concludes that the evolutionary psychological explanations are threatened, writing, “The fact that some gender differences can be manipulated, if not eliminated, by controlling for cultural norms suggests that the explanatory power of evolution can’t sustain itself when applied to mating behavior.”
From the unified psychological perspective, this debate between sociocultural and evolutionary psychologists on the cause of our behavior is grossly misguided. Our position is that both sides have limited frameworks that fail to incorporate the key insights of the other side, and this, in turn, leads to straw man claims about what the other side says, resulting in lame debates and breakdowns in communication. Here are a couple of key principles to keep in mind from getting sucked in to this debate in a bad way.
1. Everyone agrees that the nervous system is a plastic system that acquires behaviors in context, and that no complex human behaviors (like dating) are reducible to evolved instincts in the “fixed action pattern” sense of the word. Many social scientists, like Slater, create the straw man that evolutionary explanations mean such behaviors “take on the immutability of a physical trait – they come to seem as biologically rooted as opposable thumbs or ejaculation”. This is a ridiculous claim. Any sophisticated evolutionary psychological argument takes the form of a “learning preparedness” argument, meaning that evolution predisposes individuals to have certain inclinations toward values, reinforcement and goals and that they will, all things being equal, tend to learn certain patterns over others.
2. Evolutionary psychologists are often guilty of storytelling. Evolutionary psychologists too frequently engage in the pattern Slater points out, which is that they start with a possible observation of current human behavior (say, for example, males seem to be more jealous of females sexual infidelity), then they develop some possible evolutionary explanation (female infidelity was more threatening to inclusive fitness than male infidelity), then they develop some novel experiment to test whether males are more jealous than females, and, upon finding that, argue the evolutionary explanation was supported. This is BS. The only thing that was supported was the original observation. To actually directly support the claim, one would need to go back in time and measure the jealousness of various males and females and see if that tendency influenced reproductive success. Of course, that is essentially impossible to do.
3. Evolutionary psychologists have not been effective in spelling out the learning preparedness argument. In many ways, evolutionary psychology got defined against behavioral learning theories and socialization theories, resulting in unnecessary fragmentation. Critics like Slater get away with the straw man instinct portrayal because evolutionary psychologists have not attended or explicated clearly how the nervous system is a learning preparedness system. Instead, because old learning perspectives emphasized general learning patterns, evolutionary psychologists tended to be defined against the behaviorists. This is a mistake. A part of the unified theory, Behavioral Investment Theory, explicitly articulates how evolution can be blended with learning theory.
4. Evolutionary psychologists have been even weaker in understanding the relationship between evolutionary forces and culture and socialization. The early founders of the evolutionary psychology approach, Leda Cosmides and John Tooby, argued forcefully against any domain general learning device, claiming that such a capacity would never be selected for because there was no domain general problem. They turned out to be basically incorrect here. There is a domain general social problem that emerges as a function of language. It is called the problem of social justification, which is the problem of giving reasons for our behavior. The unified theory explains how the human self-consciousness system evolved as a reason giving (justifying) system, and how this sets the stage for the evolution of human culture. For a similar argument, see Roy Baumeister’s The Cultural Animal.
Let’s return to the topic at hand, differences between men and women in their tendencies to engage in casual sex. The way the unified theory frames the issue is to first determine the evolutionary logic. Is there a good evolutionary logic that males and females would be prepared to invest differently in casual sex? The answer here is absolutely yes. Why? As Slater mentions, Trivers’ Parental Investment Theory provides a clear answer. In terms of “genetic payoff” (i.e., genes in the next generation), an offspring is of equal value to the mother and the father. However, in terms of investment for that payoff, in the case of casual sex, it is clear that the woman will “pay” much more in terms of risk, calories, action effort, and so forth. From this very basic perspective, we can say that, all things being equal, the male gets the significantly better deal. This makes a very clear prediction about how males and females IN GENERAL (i.e., at the population level) will view casual sex. For example, since humans have invented money as a symbol of human investment, we can ask the basic question, which sex would be more likely, given the above set up, to pay the other for sex? Parental Investment Theory is very clear. It predicts males will be much more likely to pay females for sex than the reverse. Now look around and see what cultures have money and see if that trend holds as a general pattern. Surprise, surprise, males tend to pay females for casual sex across virtually every culture examined.
This is the proper way to understand evolutionary forces. But you must also understand that these forces are “distal” and that they are mediated via learning (experienced patterns of investment over the course of the individual’s lifetime) and socialization (the shared beliefs and values of what are legitimate). If you have this perspective, it will not surprise you at all to learn that many men will be very reticent to engage in casual sex, either out of experiences or internalized justification systems that they were socialized in, and that the reverse will be true for many woman.
Armed with the right understanding of evolution, investment and justification, we can move past the old nature-nurture dichotomies and toward a much more sophisticated view of the human condition.