You win, I win

Philip Kitcher

• Unto Others: The Evolution and Psychology of Unselfish Behaviour by Elliott Sober and David Sloan Wilson
  Harvard, 400 pp, £18.50, May 1998, ISBN 0 674 93046 0

Organisms that contribute to the reproductive success of their species by doing things that decrease the size of their own brood appear to be inevitable losers in the Darwinian struggle. Since the 19th century, biologists have regarded the evolutionary possibility of altruism as an important theoretical puzzle, and in past decades, it has become clear that it can’t be solved by vague appeals to the idea that co-operative behaviour is good for the flock, the herd or the species. There are alternatives, however. If altruists direct their helpful behaviour towards relatives, then the genes associated with altruism may spread, because they are present in the beneficiaries and transmitted to their offspring; or if today’s altruist is tomorrow’s recipient, the present loss may be made up with interest. Models of kin selection and reciprocal altruism are widely regarded as solving the puzzle.