A phylogenetic analysis of breeding behaviour in birds shows that cooperation is more likely when promiscuity is low — a circumstance in which helpers can be more certain that they are offering aid to relatives. Intermediate levels of promiscuity favour the ability to distinguish relatives from non-relatives. At high levels of promiscuity, no form of cooperation is favoured. Levels of promiscuity therefore provide an explanation for differences between species in levels of cooperation.
- Charlie K. Cornwallis
- Stuart A. West
- Ashleigh S. Griffin
