On the Evolution of Altruistic Ethical Rules for Siblings

-This paper explores the evolutionary foundations of altruism among siblings and extends the biologists’ kin-selection theory to a richer class of games between relatives. We show that a population will resist invasion by dominant mutant genes if individuals maximize a ‘‘semi-Kantian’’ utility function in games with their siblings. It is shown that a population that resists invasion by dominant mutants may be invaded by recessive mutants. Conditions are found under which a population resists invasion by dominant and also by recessive mutants. (JEL C70, D10, D63) Most economic models are inhabited by selfish consumers, although in the ‘‘economics of the family’’ it is permissable for parents to care about their offspring and perhaps also their spouses. Typically these models treat preferences for selfishness or altruism as axiomatic rather than deduced from a more fundamental model of human nature. In recent years there have been interesting efforts to find deeper roots for consumer theory, drawing conclusions about the nature of human preferences from the evolutionary history of our species. Gary Becker’s (1976) investigation of the evolutionary foundations of the family and Jack Hirshleifer’s engaging manifesto (1978) on behalf of an evolutionary basis for preferences were pioneering efforts. Robert Frank (1988) discussed the evolutionary origins of emotions, Ingemar Hansson and Charles Stuart (1990) and Alan Rogers (1994) discussed the evolution of time preference and attitudes toward saving and work effort, Arthur Robson (1992a,1992b) suggested a theory of the evolution of preferences toward risk, and H. Peyton Young (1993) developed an evolutionary theory of social conventions. Evolutionary biologists such as William Hamilton (1964a, 1964b), Richard Dawkins (1976), John Maynard Smith (1978), and Robert Trivers (1985) have investigated the theory of kinselection--the evolution of altruistic behavior between close relatives. Dawkins’ evocative expression of this view in The Selfish Gene, is that in evolution, the replicating agent is the gene rather than the animal. Since a gene carried by one animal is likely to appear in its relatives, it follows that a gene that makes an animal help its relatives, at least when it is cheap to do so, will