I’d Save Two Brothers, Not One

According to legend, one night in the 1950s while drinking at a pub in the West End of London, [Biologist and neo-Darwinist J. B. S. Haldane ] was presented with a philosophical question: How far would you go to save the life of another person? “I would jump into a river to save two brothers, but not one,” Haldane said after feverishly calculating on the back of a napkin. “Or to save eight cousins but not seven.”

However, Haldane’s drunken calculation may have pointed to a way out of the “altruism conundrum” for evolutionary psychologists. If a person performs a selfless act for someone in their own family, they are still promoting the survival of their own DNA, right? Sociobiologists in Western Europe decided it can only be explained among people and organisms who were related by blood.