Green-beard effect

The green-beard effect is a thought experiment used in evolutionary biology to explain selective altruism among individuals of a species.

Green-beard alleles are vulnerable to mutations that produce the perceptible trait without the helping behaviour.

Altruistic behaviour is paradoxical when viewed in the light of old ideas of evolutionary theory that emphasised the role of competition.

Since genes are invisible, such an effect requires perceptible markers for altruistic behaviour to occur.

The concept remained a merely theoretical possibility under Dawkins' selfish gene model until 1998, when a green-beard allele was first found in nature by Laurent Keller and Kenneth G. Ross in the red imported fire ant (Solenopsis invicta).

[8] In 2006, green beard-like recognition was seen in the cooperative behavior among color morphs in side-blotched lizards, although the traits appear to be encoded by multiple loci across the genome.

[9] A more recent example, found in 2008, is a gene that makes brewer's yeast clump together in response to a toxin such as alcohol.

[10] By investigating flocculation, a type of self-adherence generally present in asexual aggregations, Smukalla et al. showed that S. cerevisiae is a model for cooperative behavior evolution.