One of the complaints that I have heard about evolutionary psychology is that it is hogwash because you can come up with an explanation for almost any behavior; that is, given practically indistinguishable environments, you can explain why someone always does (a) or never does (a). It doesn't lend itself to falsifiable predictions.
The problem here is that this is confusing micro-evo psych and macro-psych. Miro-evo psych is the attempt to find "natural selection" explanations for specific behaviors or to come up with general rules for what behaviors different circumstances will produce.
Macro-evo psych, on the other hand, is the simple statement of these four principles:
(1) Much of human behavior is geared toward the natural drive to reproduce one's genes.
(2) Much of human behavior is influenced by one's genes, and therefore genes that influence behavior that leads toward reproductive success tend to predominate. It is through this mechanism that survival/reproductive strategies become partially hardwired into us.
(3) Successful survival/reproductive strategies are partly consciously chosen and reasoned out. They are partly influenced by society. But they are partly driven by instinct that is largely genetic.
(4) The genetic/heritable components of behavior will persist despite changes in culture and environment for as long as the genes do.
Although it is not a principle of evo-psych per se, the major policy implication of evo-psych is that any social policy aimed at changing behavior needs t take into account how much of that behavior is hardwired and then figure out the best way to deal with the fact of this hardwiring. Moreover, any social policy at all must take this hardwiring into account when one is trying to work out the policy's implications.
That is all.