Altruism is defined as an action that, on average, decreases the lifetime direct fitness of an actor and benefits one or more recipients. The altruism of insect workers has puzzled researchers for decades. Altruism in nature is nowhere seen as plainly as in insect societies, in which the workers sacrifice most or all of their direct reproduction to help rear the queen’s offspring. How did natural selection, which normally favours increased reproduction, cause individuals to help others at a cost to their own reproduction? This is a controversial topic which has recently caused a public argument between Richard Dawkins and E.O. Wilson.

Inclusive fitness theory suggests that high relatedness has been key in promoting such altruism. Recent theory, however, indicates that the intermediate levels of relatedness found within insect societies are too low to directly cause the extreme altruism observed in many species. Instead, recent results show that workers are frequently coerced into acting altruistically. Hence, the altruism seen in many modern-day insect societies is not voluntary but enforced. Prof. Ratnieks will also discuss the role of coercion in promoting altruism and cooperation in other social systems, such as vertebrate and human societies.

Francis is Professor of Biology and Environmental Science at Sussex University.