Promiscuity and the evolutionary transition to complex societies


Theory predicts that the evolution of cooperative behaviour is favoured by low levels of promiscuity leading to high within-group relatedness1,2,3,4,5. However, in vertebrates, cooperation often occurs between non-relatives and promiscuity rates are among the highest recorded. Here we resolve this apparent inconsistency with a phylogenetic analysis of 267 bird species, demonstrating that cooperative breeding is associated with low promiscuity; that in cooperative species, helping is more common when promiscuity is low; and that intermediate levels of promiscuity favour kin discrimination. Overall, these results suggest that promiscuity is a unifying feature across taxa in explaining transitions to and from cooperative societies.

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Figure 1: The monogamy hypothesis.
Figure 2: Making sense of the diversity.
Figure 3: Promiscuity and cooperation.
Figure 4: Promiscuity and the transition to and from cooperative breeding.
Figure 5: Kin discrimination and rates of promiscuity.


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We thank J. Hadfield for statistical advice, K. Boomsma, S. Nakagawa and B. Sheldon for comments and discussion, M. Nelson-Flower and P. Brennan for access to unpublished data, and the ERC and Royal Society for funding. The compilation of our data set was made possible by access to the collections of the Alexander Library.

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All authors contributed extensively to the work presented in this paper.

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Correspondence to Ashleigh S. Griffin.

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The authors declare no competing financial interests.

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Cornwallis, C., West, S., Davis, K. et al. Promiscuity and the evolutionary transition to complex societies. Nature 466, 969–972 (2010).

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