Adopting adoption.

The common occurrence of adoption among birds and mammals presents evolutionary biologists with an explanatory challenge. The benefits to adoptees are self-evident, but the benefits to the adopter(s), the origin of the set of behaviours that constitute 'adoptive' behaviour, and the conditions for its spread in populations are not always clear. Explanations in terms of direct and indirect benefits to adopters and adoptees, and in terms of conflict between them have been suggested to account for the current functions and the evolutionary origin of 'adoptive' behaviour. In this paper we emphasize one aspect of the parenting behaviour associated with adoption that has been neglected: we suggest that adoption in birds and mammals is a route for the transfer of learnt information through social learning of patterns of behaviour, including styles of parenting. By using simple models we show that learning parenting from non-parents may provide additional opportunities for the spread of the 'adoptive' behaviour itself, even when it has no selective advantage. We also offer an additional explanation for the adaptive significance of adoption for both adopters and adoptees. Our 'match-making' hypothesis suggests that in some cases, by adopting foreign young, parents provide their genetic young with future ecologically compatible, but genetically unrelated, mates. Copyright 1998 The Association for the Study of Animal Behaviour. Copyright 1998 The Association for the Study of Animal Behaviour.