In the post below, I referenced a Fresh Air interview with Richard Dawkins. While I found him very interesting and compelling, I was disappointed when he fumbled the question of whether evolution is poorly compatible with a sense of morality. I've had debates with friends in which they have claimed that we have been imbued by God with morality and without a basic gut feeling of right and wrong, a divine moral compass, we would devolve into a murderous animistic chaos.
Dawkins response to this was convoluted. He stated that it was an accident of evolution. It was an advantage to treat those in our tribe justly and to fear the others. However, as time progressed, the tribe became larger and larger and the other has become smaller and smaller. Thus, we treated nearly everyone like members of the tribe. I find this utterly unconvincing.
I think a more sensible evolutionary explanation is the development of logic and reasoning by humans, which has allowed us to achieve many great things as well as provide an amazing survival advantage. Once reasoning is achieved, morality follows. If you want to have a civilized and operating society which benefits everyone and maximizes survival, there are certain logical rules that we all generally agree upon. Murdering someone feels wrong not because God inserted this feeling in our gut, it feels wrong because permitting murder does not make sense. Things that do not make sense generally make me queasy. This includes murder, some quantum physics, and belief in the supernatural.
Morality is not accident, it is also not dependent of God (in a raucous takedown, Christopher Hitchens shows here that the Ten Commandments are incomplete and have no monopoly of moral thought). It is an evolved trait, one that will help perpetuate the species.
Bonus link: As this TED presentation, Steve Pinker provides a compelling history demonstrating that humanity is becoming less violent with time, despite the doom and gloom about the current time.