The three brothers' problem: kin selection with more than one potential helper. 2. The case of delayed help

The evolutionarily stable strategy of helping behavior is studied in situations involving a single relative in distress and several potential helpers. Cases are considered in which no immediate help is mandatory, and at each moment every potential helper has full information on the response of others. Although it seems always advantageous to leave the risky job of providing the needed help to any of the other potential helpers, it turns out that if Hamilton's condition for one-to-one altruism is met, the evolutionarily stable strategy is usually a mixed strategy of altruism and selfishness, characterized by a positive probability of helping. -Authors