Gardner A (2019) The greenbeard effect. Current Biology 29, R430-R431.
What is the greenbeard effect? The greenbeard effect is a driver of social evolution, and one of the three basic mechanisms of kin selection. It was first described in the 1960s, in the context of W.D. Hamilton’s work on the evolution of altruism and other social behaviours. Hamilton noted that a gene encoding altruistic behaviour, and hence reducing the fitness of its carrier, can nevertheless be favoured by kin selection if the individuals who benefit from the altruism also carry copies of the same gene. The first two mechanisms of kin selection (kin discrimination and population viscosity) involve the beneficiaries of altruism being genealogically close kin of the altruist, whereas the third mechanism (the greenbeard effect) can operate even when the altruist and her beneficiaries are not genealogical kin.