Recently I went through an informative talk on Evolution of Altruism by Lee Alan Dugatkin. (Link to talk, link to summary post). He traces the problem faced by evolutionary biologists to explain the phenomenon of altruism. Eventually he presents the formula given by W.D. Hamilton -

r B > c

r - Genetic relatedness
B - Benefit from act of altruism
c - Cost associated with the act of altruism

It's a remarkably simple and elegant explanation for altruism.


PS. If you are interested in full explanation on altruism from evolution's perspective, watch the PopTech's PopCast. Link again.

The quote I like the most from the talk is following -
Reporter: "What can evolution tell us about God?"
Haldane: "God must have an inordinate fondness for beetles"