The selection of social actions in families: I. A collective fitness approach

Here I analyse the basic properties of relatedness, inclusive fitness and k in selection, and derive alternative ways of formulating the selection of s ocial behaviours. In particular, a 'collective fitness' rule is sought, whi ch determines the direction of selection on a gene in terms of the effect a n act has on the fitness of various individuals in a population, and the nu mber of copies of the 'action' allele in various individuals in the populat ion. The use of collective fitness allows for all the simplifications in ki n-selection explanations of social behaviour that use inclusive fitness In addition, it covers analyses of social behaviours in which factors other th an kinship influence the distribution of genes in interacting individuals, without invoking an open-ended expansion of the concept of 'relatedness'. T he treatment of social actions ends with a discussion of how far the concep ts of relatedness, inclusive fitness and kin selection should be extended w hen factors other than kinship contribute to the distribution of genes to a ctors and recipients.