It has been suggested in comments on my previous post that an evolutionary theory of norms is "purely descriptive," at most a basis for an error theory. There is certainly something to that. An evolutionary theory is, or at least should be, far closer to a skeptical theory than to a typical magical theory. Evolution has no authority over us; discovering that we have evolved to have this or that concern does not provide an additional reason for having that concern, it only explains why we have it.
Even the explanation of why we have it can get very complicated on the evolutionary story, and the evolutionary story is quite well able to explain how we could come to have goals which are counter-productive from the point of view of survival or reproduction. Even apart from the possibility that some of our systems might be defective (in the sense of being unsuited to their evolved functions), or appropriate for a different environment than that we presently occupy, there is the further point that there are many levels of intermediate functions between the goals of DNA and our goals. That at one level of analysis we pursue goal D because of its connection to the pursuit of goal C at a deeper level, and that this in turn is because of goal B at a still deeper level, which is because of goal A at the next level after that, in no way means that goal D can be collapsed to goal A, and goal D may indeed be quite different from goal A. With enough levels, there may be Ds which are consistently opposed to the original As. At some point, if too many of the higher level goals are too poorly coordinated with the goals of the DNA, that is going to produce the extinction of the species, but that sounds to me like a decent enough description of what often happens to cause species to go extinct.
Of course, it is wildly implausible anyway that evolution would tell us what we should value. Such suggestions are far more often found in straw evolution theorists constructed by magical theorists (whose theories do tend to claim to be able to tell us what we should value, and who imagine any theory must be trying to do the same) than in any claims made by actual advocates of evolutionary theories of normativity.
It seems to me that the very thin, perhaps purely descriptive (if there really is any such thing as being purely descriptive), account of normativity from evolution is nonetheless sufficient for the only critical purpose, making our beliefs and desires intelligible. For anything more, I am quite in sympathy with much of the non-cognitivist and error-theoretic tradition. Nothing has the sort of authority over us that most magical theories claim to have. While some norms can be justified instrumentally, of course, on the basis of other norms, at some point it stops making sense to ask why a norm has force for us, and this is not because the force is somehow inherent. Rather, we either care about the norm, or we don't; if we care, we don't need a further reason, as our concern is motivation enough, and if we don't care, that norm has no power over us. Even some who otherwise appear to be magical theorists seem to recognize this. Plato doesn't seem to believe that there is any way to reach a Callicles.