(UPDATE: I've added an important thought that I forgot to put in before. Look for it below)
I've recently read a rather good paper by John Hare about the failings of evolution to explain morality. His paper pretty much aligned with my prior intuitions, but he obviously explained what the problem was much better than I had every been able to. The main problem is this: there is a moral gap between what we ought to do and what we can do. If ought implies can, as many people believe, then we are only obligated (morally speaking) to do what we can in fact do. So if ought implies can, then what we ought to do will, seemingly, be considerably constrained by what we have the capacity to do. Herein lies the problem. If we can't live up to morality (as is evidenced by, well, everyone everywhere), then how can we be morally responsible for our failure? You can only be responsible for what you have the power or capacity to accomplish, and it seems that our moral capacity falls rather short of our moral obligations. The question is: can evolutionary theory provide any help in bridging this gap? Hare thinks no, and I agree. Here's why...
So we'll start by fleshing out Hare's moral schema. He traces the origins of his view way back to some medieval folks, but we'll skip the history lesson. The important part is that we have two different affections, or inclinations. The one affection is called the "affection for advantage" where advantage can be defined, roughly, as self-interest. This affection is pretty obvious to everyone. We are often motivated by our own desires, and many of our actions are results of this motivation. The second affection is the "affection for justice" where justice is, for the most part, the recognition that other moral beings carry as much weight as the self, so the self cannot be promoted above those other beings. Self-sacrifice, altruism, and all that jazz fall into this category. Now, Hare doesn't say that first affection is inherently bad. It can be a good thing. What Hare does say is that the affection for advantage must come second to the affection for justice. In other words, the first affection isn't bad so long as it is subordinated to the other affection. Now that that's clear, an obvious problem arises. The ranking of affections ought to be one way, but humans, by and large, come with the ranking reversed. Not only is the ranking reversed, but it's super hard to switch around. In fact, it's impossible for us to live with the proper ranking.
And that's the problem. If we can't live with the proper rankings, at least we haven't proven thus far in the course of history that we can, then it's hard to say we ought to. Remember, we only ought to do what we can do, and if we can't switch the rankings then we can't very well be obligated to do so. This is the performance gap. We can't do it, but our sense of morality says that we ought to. Yikes. What now? Well, Hare would say that the theist approach (in his case, the more specific Christian approach) offers a bridge. Yes it's true that we can't switch our rankings alone, but we still ought to because it is possible for us to do if we get help from God. Ought is still in, because we can if we get some support from the Big Guy. Well, that makes sense. We clearly can't live up to moral obligations on our own, but we still ought to, so maybe there is a way that we can and that way is by getting help from God. God is the bridge between our actual performance and how we ought to perform.
So what's the problem then? Well not everyone buys into the God bit, so there is still that nasty problem of can't. Can't takes away our ought, and we want to keep the ought (well, some of us do). We want to be able to say that mass killing is wrong and that slavery is bad. We want to because we have this deep sense of ought, and no matter where the ought came from we want it to mean something. But can it mean something if it's a product of natural selection?? This is where Hare recognizes 3 strategies that are often used to bridge the gap sans God:
1. Lower the moral standard
2. Exaggerate our capacity to meet the standard
3. Find a substitute for God's help (a new bridge)
The first solution is the one Hare treats at length in his paper. It's the one I think most people are tempted to buy into. If you never fail morally, then you've met the standard, and that standard is perfection. Perfection, you might then say, is too high a standard. Let's lower it to be "good enough," or something like that. (This wasn't talked about by Hare, and I'll get back to his critique momentarily) My problem with that is: what is good enough? Perfection is an easy line to draw. Good enough is messy. Where does it go, and can it even be one line? Is there a range, and can only one moral failure knock you out of that range? This suffers from the "no sharp distinction" problem (hair on head, pile of sand, say what you will). There is no way to judge where that lowered standard should be drawn. So then maybe you'd clarify it and say, well you are only responsible to be as good as you can possibly be. That too poses some problems. What if Hitler was a good as he could possibly be (taking into consideration environmental factors, genetics, etc)? Does he then have no moral blame for his actions?? I doubt it. The truth is, lowering the standard is really just making things even harder, and no bridge is being built. Instead we're just saying that we're content to sit on the moral failure cliff.
(UPDATE: I forgot to mention that perhaps the standard could be considered not as an all things considered measure but in a case-by-case basis. If we can do the right thing in each particular instance --which is evidenced by the fact that we sometimes do-- then the can survives and the ought does too. It's not until you look at morality as an all-choices-taken-together standard that it looks so bleak. Or maybe it still looks bleak case-by-case. I suppose you could also say that while it's highly improbable that we will be morally perfect, it is possible. If in every situation we could do the right thing, then in every situation we ought to. All because it's highly unlikely that we will always do the right thing, and all because no one else ever has in the past, well that doesn't necessarily mean it's impossible. You could offer Jesus as an example if you were so inclined. It's possible. In that case, we still ought to even though there's not a very good probability that we will live up to the ought. But still, this grim probability verges on the border of can't so I'm not sure. In this case we are responsible, bridge or no, for getting to the other side. It's sort of a depressing set-up, but you could roll with it if you really want to keep ought without the help of God.)
Hare sees the lower standard as a rejection of the affection for justice. Evolutionary psychologists try to pin morality on a naturally selected trait that will increase the survival of our species. That being said, morality must then be based on self interest, or affection for advantage. Affection for justice essentially disappears. In this way the standard is lowered so far that morality really just means our affection for advantage. That's it. And that's pretty depressing. Hare clarifies it with this example: "To see the effect of Arnhart’s view [a guy who proposes this sort of compromise], consider the case of slavery. Arnhart is not entitled to condemn it morally, since it results from the satisfaction of natural desires for dominance, and he thinks the satisfaction of natural desires is good. The most he is entitled to say is that slavery is tragic, since it results from the conflict of natural desires between the masters and the slaves." To me, and to Hare, this is unacceptable. Slavery is not just tragic, it is morally reprehensible. If you can't condemn slavery, or similar evils, then why speak of morality at all??
It's clear that evolution, in this case, is not building a bridge. It's merely deciding that getting across the gap is either not something worth pursuing, or it's nonsensical because there is no other side to get to. Now Hare mentions a point here that I think is not made enough, and it's that evolution need not be a complete explanation of all that there is. Why should evolution think that it must explain morality? If it can't, that doesn't mean that it's a failure as a theory; it just means that there are limits to what it can speak to. Evolution can't explain mathematics (certainly Pythagoreans theorem was not invented by man to ensure our survival --recognized by us maybe-- but we don't invent mathematical truths). Evolution needs to stop trying to over-explain things. Hare says: "[The] view [held by some guy called Alexander] is that humans invented mathematics, and therefore mathematics has to be understood fundamentally in terms of genetic self-promotion, just like religion or any other feature of life. But then this claim is no longer a part of the theory of evolution, but it is a metaphysical view added onto it: that every domain above the physical and the chemical which human life encounters is to be explained ultimately by natural selection at the genetic level. It is important to see that this metaphysical view cannot itself be justified biologically; it is, I believe, an article of faith for Alexander, though it is not recognized as such."
And there's the key: evolution can only be a complete world explanatory theory if taken on faith by it's proponents to be all that there is. That doesn't mean evolution can't explain some things; it just means that when you try to say evolution can explain all things you are taking a metaphysical leap of faith that you can't back up with your theory. So there's something to think about.
Another concern is the publicity standard. If people lose the willingness to conform to some standard after discovering the true foundation of that standard (or lack thereof), then that standard has a pretty big strike against it. Example, if I am nice to my sister because my mom says that Santa will give me coal otherwise, and if I then find out that Santa isn't real, then I loose a big motivation to be nice to my sister. In fact, I probably won't be very nice if that was the only reason I bothered to be nice in the first place. If you take away the foundations of morality, then people won't be bothered to follow it. And why should they? If morality is really only a manifestation of self-interest, then why bother? Why not just promote the self at all costs if that's where morality stems from anyway? That's a problem.
So evolution is looking grim as far as finding a bridge for the moral gap goes. It just can't, on it's own, get us from one side to the other without making things more complicated. At best you can just decide not to worry about, and at worst you can abandon objective morality all together (which is getting more popular to do). There was way more in the paper, and you should read it, but I'm out of space/time for now. More later if I have the chance.