Evolutionary psychology has many problems because they want mechanistic explanations cheaply. The worst of evolutionary psychology occurs when they explain a more complex social behavior as fully represented by the cheap mechanistic trick. Cheap tricks, or simple mechanistic maneuvers, are useful in evolutionary terms for changing and controlling behavior. Often, as long as the behavior is created a good portion of the time, then whatever mechanism gets applied will be adequate, from an evolutionary perspective. The evolutionary psychology program can give us many accounts for animal behaviors, though certainly with some social and situational processes there may be a complexity that gets covered over, or that becomes inexplicable when we get to real life animal behaviors.
When we get to human behaviors, some of these stories, that are underwritten by some kind of mechanical process, can be useful in describing behaviors. Certain mechanisms probably have shaped social institutions and they are still structuring behavior to some extent. There is a complex dialectical process, either within institutional development across a society or in the development of individuals as they are shaped by any institutional/social matrix. Mechanisms that encouraged behaviors at earlier times have been in constant relationship with those social dialectical processes, that is, they constantly and continuously create some kind of effect.
One example is the sugar explanation. The idea is that we have pleasurable sensations from eating sugar, and that this arises because sugar is high in calories and would have benefited individuals who ate more of it. Mechanistically, we can probably (eventually) tell some story about the baseline structures of taste receptors and brain functions that make that story true. Human tastes can be complicated by social factors (e.g., conditioning), but there is good reason to believe that such a mechanistical tale will make some sense, in a similar way that sex is so pleasing because of the needs of reproduction. The problem arises, however, as we explain our institutional sugar use (the products created, the refining of it, the marketing of it, etc.). And also as we try to explain any individual's intake of sugar. An individual sits within an environmental setup (say cheap sugar from the gas station), and also has been created by a long developmental process, thus the structure of their brain/mind at the time that they choose to intake sugar. A repeated process of sugar intake or sugar refusal by the individual we can read as the “trait” of sugar intake. The problem is that what that “sugar trait” is at any time can be made far different given a different institutional setup, as well as a different developmental process. This may mean that the individual, the self, we are seeing within one social system and one developmental history may be a completely different self or identity than the one made under largely differing conditions. Both individuals may have similar mechanistic processes in response to sugar on the tongue, but the behaviors, the thoughts, the choices being made can be radically different between the same set of genes (general body structure) within those two different worlds. Thus there is a distance between the mechanistic process and the trait of a given individual.
We can see some of this by telling the same story about the “cocaine trait.” Most of us today have a far different cocaine trait than we do sugar trait. Though different, we can probably say that both sugar and cocaine have some strong pleasure-inducing sensation, I assume. The institutional structures (product availability, general norms around use) and developmental programs mean that the pleasure-inducing sensations of these two substances lead to two different “traits” in most of us. Though I doubt we will go that far, it is possible to imagine a society that would try to make most people's sugar trait be similar to most people's cocaine trait today. Part of doing that may be through demonizing sugar, like we do with cocaine, but it may be by strong prohibition like factors of denying supply.
Evolutionary psychology gets in trouble by overstating the necessity and indelible nature of our institutions and our brain/minds as regards choice making, hence our traits. They often ignore the historical social dynamics that lead to any matrix of institutions and character development, that thus produce the brain/mind as it engages with a present environmental condition, say a woman “desiring” a tall man. The mechanistic story, that they buy rather cheaply, that is, without actually understanding or stating the mechanistic process, gets confused for more complex behavioral programs. Yes, often times those more complex behaviors have been guided and shaped by the simpler mechanistic origins, but evolutionary psychology often presents the complex behavioral phenomena as we should be presenting the indelible, underlying mechanistic force. Some of this also has to do with the age we are living in, which is one that often proclaims certain social factors (say capitalism, gender and family structures) as unchangeable social givens. If we take certain institutions and developmental structures as given, then the simpler mechanistic forces can look one and the same as the latter complex behavioral activity.