When having a conversation with my friends who do not study evolution, I often end up having the following exchange. Someone will be discussing a phenomenon that makes evolutionary sense, for example, men's greater interest than women's in casual sex. I will point out that this phenomenon does, in fact, make evolutionary sense. Then, my conversational partner will make a statement starting with the phrase "Yeah, well, is that evolutionary, or is it...?" Using the example of men's interest in casual sex, it might go something like "Yeah, well, is it evolutionary, or is it socialization?"
Other examples of this conversation that I can remember having recently include discussions of sex differences in general ("Is it evolutionary, or is it cultural?"), people's love for babies ("Is it evolutionary, or is it that babies are just cute?"), and menstrual cycle effects on behavior ("Is it evolutionary, or is it hormonal?").
These questions all assume that whatever mechanism my conversational partner suggests is actually an alternative explanation for evolution. However, this is not true. Our ability to learn and the motives underlying what we try to learn, what we perceive to be cute, and hormones and our responses to them are all examples of human characteristics that are not only "evolutionary" (a term which encompasses many different types of explanations for things), but that have undergone intense selection.
There is no reasonable alternative to natural selection that humans should find babies and not, say, tarantulas, to be cute: Those individuals who perceived babies and tarantulas to be equally cute failed to reproduce at the same rate as those who did not. Nor is there a reason that women should react in some ways to reproductive hormones and not other ways. Our cultural practices (e.g., incest taboos, violent male contests) often clearly reflect our adapted psychologies.
This misunderstanding is caused by a failure to discriminate between levels of causation. Levels of causation are not specific to discussions of evolution: If I asked you why a car moves and you told me it was because engineers had designed it to move, you would be no less correct than if you had said the car moved because I pressed the accelerator. Evolutionary researchers discriminate between causes that occur during the lifespan ("proximate" causes, such as learning, cuteness, and hormones) and evolutionary causes ("ultimate" causes, such as that those individuals who didn't perceive babies to be cute were less likely to care for their babies and subsequently less likely to pass on their genes).
A problem facing those who criticize the use of using evolutionary theory to solve problems about behavior is that evolution has no mutually exclusive alternative, at least not one that is both falsifiable and yet unfalsified. Whether or not academics often take an evolutionary perspective in their research, understanding the proximate-ultimate distinction and, more generally, the concept of levels of causation will promote clear and productive thinking.
