The Evolution of Cooperative Breeding in Vertebrates

Cooperative breeding in which some sexually mature individuals forgo independent breeding, join a group as subordinate and help to raise the offspring of others occurs in at least 3% (mammals) and 9% (birds) of vertebrates. Because helping others is costly, this behaviour contradicts the concept of selfish natural selection. The intriguing evolutionary paradox of such seemingly altruistic behaviour has, therefore, been the focus of much study aiming to unravelling the evolutionary drivers underlying cooperative breeding. The benefits of group living, costs of dispersal and constraints of limited available independent breeding positions may persuade individuals to delay independent breeding and remain as subordinates within a group. However, it is the range of subsequent benefits (indirect benefits such as improving reproduction and survival of related individuals or direct benefits such as gaining breeding experience, benefits of future cooperation with raised recruits or gaining a share in reproduction) that favour the evolution of helping.