Inclusive Fitness - Green-Beard Effects

Green-Beard Effects

As well as interactions within reliable contexts of genetic relatedness, altruists may also have some way to recognize altruistic behavior in unrelated individuals and be inclined to support them. As Dawkins points out in The Selfish Gene (Chapter 6) and The Extended Phenotype, this must be distinguished from the green-beard effect. The proposal that altruists who support other altruists who are not their kin will encourage the evolution of altruism requires that altruists recognize and choose to support others predisposed toward altruism whom they have detected by their past altruistic behavior, not on the observation of some temporarily correlated characteristic (e.g., altruists have green beards). If the green beard effect were the mechanism, some non-altruistic individuals would evolve to mimic the label and would receive the benefits of support from altruists. This would happen quickly due to crossing over of chromosomes; it would not require waiting for the rare event of a mutation. The mimics would receive the benefits but would not incur the costs of caring for others, and so would out-compete the true altruists. Green-Beard transfers thus have a negative affect on the evolution of altruistic behaviors.