To begin with, we know very little about the specific adaptive problems faced by our distant forebears. As Buller points out, "We don't even know the number of species in the genus Homo"—our direct ancestors—"let alone details about the lifestyles led by those species." This makes it hard to generate good hypotheses. Some EP-ers have suggested looking to modern-day hunter-gatherers as proxies, studying them for clues about our ancestors. But this doesn't get them far. For instance, in some contemporary African groups, men gather the bulk of the food; in other groups, women do. Which groups are representative of our ancestors? Surely there's a whole lot of guesswork involved when evolutionary psychologists hypothesize about the human brain's supposedly formative years.Very clever! Are they right? No idea. Though I think Schaffer's question about why evolutionary psychology remains so popular among pundits seems a bit naïve. Maybe becuase it offers a splendid little excuse to wave away social problems such as, say, gender inequality in the workplace. Don't bother doing anything about the problem, just note: "But since the dawn of bipedalism, men have always been more competitive!" And then shrug. Now it might be true that men actually evolved to be more competitive and this is some fixed and immutable fact of existence—damned if I know—but it's of course impossible to say how true this really is, and how much it accounts for, say, fewer female executives, and how much owes to real discrimination. Evolutionary appeals in this situation often just amount to a bunch of hand-waving, to avoid having to tackle or think about sexism. But, for reasons that become clear when we consider the behavior of hunter-gatherers on the veldt, humans are naturally prone to hand-waving, and so this technique becomes very popular.
In addition, we are probably not psychological fossils. New research suggests that evolutionary change can occur much faster than was previously believed. Natural selection is thought to effect rapid change especially when a species' environment is in flux—precisely the situation in the last 10,000 years as humans learned to farm, domesticate animals, and live in larger communal groups. Crucially, Buller notes, in order for significant change to have occurred in the human mind in the last 10 millennia, evolution need not have built complex brain structures from scratch but simply modified existing ones.
Finally, the central, underlying assumption of EP—that humans have hundreds or thousands of mental problem-solving organs produced by natural selection—is questionable. Many cognitive scientists believe that such modules exist for processing sensory information and for acquiring language. It does not follow, however, that there are a plethora of other ones specifically designed for tasks like detecting cheaters. In fact, considering how much dramatic change our forebears faced, it makes more sense that their problem-solving faculties would have evolved to be flexible in response to their immediate surroundings. (A well-argued book from philosopher Kim Sterelny fleshes out this claim.) Indeed, our mental flexibility, or cortical plasticity, may be evolution's greatest gift.