Darwin’s theory of evolution by natural selection is arguably the most powerful idea ever to occur to a human mind. Think what it can explain (and that really means explain, in the fullest sense of the word): your existence and mine, as well as the form, diversity, and teleonomic elegance of all living things, not only on this planet but probably wherever in the universe organized complexity can be found.
The New Encyclopedia of UNBELIEF, p. 231
In ancestral times, we had the opportunity to be altruistic only towards close kin and potential reciprocators. Nowadays that restriction is no longer there, but the rule of thumb persists. Why would it not? It is just like sexual desire. We can no more help ourselves feeling pity when we see a weeping unfortunate (who is unrelated and unable to reciprocate) than we can help ourselves feeling lust for a member of the opposite sex (who may be infertile or otherwise unable to reproduce). Both are misfirings, Darwinian mistakes: blessed, precious mistakes.
The God Delusion, p. 221