‘Green-beard’ genes could explain how altruism arose in nature Premium

Altruism in nature, from worker bees to amoebae, explained through green-beard genes and self-recognition mechanisms.

Altruism is widespread in nature. Worker honey bees devote their entire life to foraging and caring for their sister, the queen, and her offspring, but do not themselves reproduce. In widow spiders, a male allows a female fertilised by him to eat him, and thus nourish herself and her offspring. A meerkat, a mongoose found in Africa, assumes the role of a sentinel, perching itself on a mound or rock, keeping a lookout for predators, instead of foraging for food, while the rest of the clan is feeding. If a predator is sighted, it alerts the others.

Many humans themselves have agreed that “greater love has no man than he who lays down his life for his friends”.

How can the emergence of altruism in all these diverse forms be explained?

Most of the progress in answering this question has come from studies of a simpler organism that has been easier for researchers to study: the social amoeba Dictyostelium discoideum. The take-home message of these studies is that if a gene makes a worker bee altruistic, it also helps the copy of the gene in the queen and her offspring to be passed on to the next generation, even if the worker herself does not reproduce.

Such so-called ‘green-beard’ genes allow the individuals bearing them to recognise and preferentially cooperate with each other.

Alternatively, a green-beard gene could provoke individuals to behave harmfully towards those carrying a different version of the gene.

Thus, scientists have postulated, green-beard genes encode some kind of tag that helps the genome to know their identity (i.e. self-recognition).