As social creatures who are gifted with large cerebral noggins who uniquely reflect on their reflections and are painfully self-conscious about it, there is however a trick or two to ameliorate all this mean spiritedness. Since we are buggered by the fact that we have consciousness, and don't know how the darn thing survives, evolves, or just moves about after we die, a whole new set of metaphors has 'evolved' that answers these timeless questions and as a bonus keep us in line. Thus the metaphors of natural selection are supplemented by the metaphors of super-natural selection. These metaphors are called religion. So if you want to survive not only in this world but the next, and not devolve into an insect (bad karma) or be perpetually squashed like one (such as in the 8th circle of hell), it pays to be kind to kittens and little old ladies.
So we embrace religion, but end up acting like selfish assholes in any event. In fact, religion can easily be used to rationalize all sorts of awful behavior. The problem arises when some armchair pundit believes this deception, and assumed that religion is not used as a general rationalization for bad behavior, but is the actual reason for that behavior. In his latest book, 'The God Delusion', the evolutionary biologist Richard Dawkins rants and rages about the endless stupidities and cruelties of religion, but forgets that if you're acting stupid and cruel, it ain't God who is behind your behavior, but rather your selfish genes. After all, if you are a Crusader, business tycoon, or just an everyday guy who instinctively loves to rape and pillage, what better way to rationalize the whole thing than by saying that God made me do it? Overall, the philosopher Nietzsche was closest to the mark when he said the last Christian died on the cross. For Dawkins, Christianity just makes him cross. Perhaps there is some poetic justice in this.