Where do atheists get their morality from?

[Red Celt]

These animals pass on their genes to their young whereas the selfish bastards die before they have time to mate. Natural selection in other words ensure that the reasonably altruistic animal survives.

Just a small correction. Reading that, it looks like you're suggesting that social altruism is a genetic hand-down. It is more likely to be cultural (nurture rather than nature), but the end effect is the same. Antisocial animals fare poorly amongst social animals.