sblinn over on reddit raises an interesting point (particularly since we have a Calvinist lurking out there somewhere):
what does it mean to now have a good working theory of evolutionary morality while not having a good working theory of the free will to exercise it? ... If all we can do is carry out the mechanisms of biology and chemistry, according to our compositions and environmental stimuli, whatever right and wrong are we will still be doing whatever it is this mechanism computes.
There are a couple of answers to this.
First, we are not completely deterministic. At root we are quantum entities. Whether or not quantum randomness actually plays any significant role in our thought processes is not known, but the possibility cannot be ruled out based on our current understanding.
Second, even if we are completely deterministic that does not mean that our actions are completely predictable because of Chaos theory.
Third, even if we were completely deterministic and predictable we somehow have the illusion that we have at least a certain amount of free will. Imagine you get up in the morning and you have to decide whether to wear the red tie or the blue one. Whether or not you actually have free will in your decision, it certainly feels like you do. But there are also clearly things over which we do not exercise free will. You cannot choose to believe that the red tie is actually green, for example. (Well, maybe you can, but I can't.)
A belief in a certain amount of free will, even if in reality it is only an illusion, is a logical prerequisite to morality, and a practical necessity for the functioning of human society. If all our actions are truly out of our control (as the Calvinists would have you believe) then there is truly no reason for morality, because then everything that happens is merely a consequence of the laws of physics or the Will of God or the Hand of Fate (all of which become indistinguishable from each other in that case, by the way). The only reason philosophy (or religion) matters at all is that we each have this sense of self over which we feel like we exercise some degree of control. Absent that, nothing matters. There is no reason to punish murderers, or, indeed, not to become a murderer yourself, because whatever happens is just the inescapable consequence of whatever is out there pulling our strings. Absent free will, there is no more sense getting morally indignant about the Holocaust than about the fact that the sun rises in the morning.