The survival chances of group members are often greater in large than in small groups. In some species, non-reproducing group members therefore help raise offspring, even if they are unrelated. In an experimental study, researchers at the University of Bern investigated this seemingly altruistic behavior in cooperatively breeding fish. Their results indicate that helping can evolve by natural selection through increased survival chances of brood care helpers by selectively increasing group size.
Cooperation is widespread in nature, most prominently exemplified by social insects like ants and honey bees, apart from humans. In social insects, cooperative brood care can be easily explained from an evolutionary perspective because helpers are related to the young and, therefore, brood care helpers are successfully passing on the genes coding for their altruistic behavior via siblings sharing a common genetic makeup. “This is different in cooperatively breeding fishes, where many of the helpers are unrelated to the dominant pair they aid in raising their offspring”, says Michael Taborsky, senior author and supervisor of the new study. So why do unrelated group members help to raise “foreign” young? A paper published in Biology Letters by Irene García Ruiz and Michael Taborsky from the Institute for Ecology and Evolution at the University of Bern, reveals how such altruistic care of young can evolve by natural selection.













