Altruistic behaviour, such as sterile worker ants caring for the offspring of their queen, evolves only between related individuals through what is known as kin selection — or so many evolutionary biologists have thought since the 1960s. They argue that the standard theory of natural selection cannot explain the evolution of eusocial groups of organisms such as bees and ants, because the sterile workers in those groups do not themselves reproduce. A two-part mathematical analysis1, published in Nature this week, overturns this tenet by showing that it is possible for eusocial behaviour to evolve through standard natural-selection processes.
Reproductive benefits: Kin selection is based on 'inclusive fitness', the idea that, for example, sterile workers can accrue reproductive benefits by helping their relatives. In doing so, they help shared genes to survive and get passed on to the next generation. This provides a route for eusociality to evolve. But Martin Nowak, a mathematical biologist at Harvard University in Cambridge, Massachusetts, and the lead author of the analysis, says, “there is no need for inclusive fitness to explain eusociality”.