Lachmann, M. and C. T. Bergstrom . Signalling games among relatives allow one but a large number of possible signalling equilibria, most of which are pooling equilibria in which different types of signallers may share a common signal. Some of these equilibria will not be too costly to be worthwhile. Available in pdf . Signalling Among Relatives.
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Bergstrom, C. T. and M. Lachmann. Available in postscript and pdf . Avital, Eytan, Jablonka, Eva and M. Lachmann. The common occurrence of adoption among birds and mammals presents evolutionary biologists with an explanatory challenge. We also offer an additional explanation for the adaptive significance of adoption for both adopters and adoptees.