Among Darwin’s lasting legacies is our knowledge that the human mind evolved by some adaptive process. After all, the human brain is even more costly to run than an internal-combustion engine these days, consuming 18 percent of the body’s energy intake while constituting merely 2 percent of its weight. We wouldn’t have such an organ if it hadn’t performed some important adaptive functions in our evolutionary past.I do have a distaste for popular evolutionary psychology, not because I don't think that a lot of human behavior is genetically defined and the result of adaptation (I do), but because the evidence for this adaptation is simply lacking.
The challenge for evolutionary psychology is to move from this general fact to some evidentially well-supported specifics about the adaptive processes that shaped the mind. But, as we have seen, the evidence needed to substantiate accounts of adaptation in our lineage during the past couple of million years is scarce. And this isn’t the kind of evidence that is likely to materialize; such evidence is lost to us, probably forever. It may be a cold, hard fact that there are many things about the evolution of the human mind that we will never know and about which we can only idly speculate.
Of course, some speculations are worse than others. Those of Pop EP are deeply flawed. We are unlikely ever to learn much about our evolutionary past by slicing our Pleistocene history into discrete adaptive problems, supposing the mind to be partitioned into discrete solutions to those problems, and then supporting those suppositions with pencil-and-paper data. The field of evolutionary psychology will have to do better. Even its very best, however, may never provide us knowledge of why all our complex human psychological characteristics evolved.
We neither know how the brain works, nor how genes influence the way it works. Nor do we have a good quantitative handle on human behavior. Some aspects of it (general intelligence, for example) are better known than others, but a lot of psychology is more akin to opinion than to deep knowledge.
So, it seems that making a convincing case for adaptation in human behavior will remain a difficult problem for some time, and evolutionary psychology must find a way to go beyond hypothesizing towards hypothesis testing. The study of present day human genetic-behavioral variation will be invaluable to that end, although it will require us to overcome the idea of the human mind as more-or-less a finished product of the Paleolithic, and accept the idea of continuing and perhaps intensifying evolution.