Why is Altruism towards Kin so Rare?


Biology Department, Princeton University, Princeton, New Jersey 08544, U.S.A.

Research Centre, King's College, Cambridge CB2 1ST, England.


When individuals have the opportunity to invest in offspring or siblings who are equally closely related and helpless, they should invest in offspring. Two reasons are proposed. Both depend ultimately on the fact that if Ego invests in kin other individuals may not behave in Ego's best interest.