According to evolutionary theory, natural selection has designed individuals to behave selfishishly; selfish individuals are likely to end up with more resources and therefore more offspring. But many species (including humans, some rock musicians, politicians, and everyday citizens among them) do co-operate.
Traditionally, scientists have explained the evolution of co-operation using the idea of kin selection. Help to relatives (who share your genes) makes sense if it means your relative will have more children who will carry your genes into the next generation. Therefore, relatives are expected to help more. However, in a study published today in the Proceedings of the Royal Society, McMaster University researchers show that in certain situations the reverse is true: unrelated individuals help more.
Sigal Balshine, associate professor of in the Department of Psychology, Neuroscience & Behaviour at McMaster and her graduate student Kelly Stiver have been studying a small species of African cichlid fish that live in groups with a dominant breeding pair and non-breeding helpers. All individuals (helpers and breeders) co-operate to defend the young and the territory. The researchers combined behavioural observations with genetic analyses of relatedness in these fish groups and found that under specific ecological and demographic conditions unrelated individuals must "pay-to-stay" in the group and therefore may help more.
"This fish species is particularly interesting because breeders and helpers are not close relatives, but they co-operate nevertheless," says Balshine. "We think that unrelated individuals may be required to "pay more" by doing m