Kinship is relative

摘要

Kinship fosters the evolution of cooperation. However, a once-heretical theory and an unconventional social organism show that the cooperation-enhancing effect of kinship is sometimes negated. As evolutionary biologist W. D. Hamilton showed more than40 years ago, selfish genes can lead to cooperation and altruism. A gene can spread by helping other individuals that carry copies of the gene. This extension of individual selection, called kin selection, works best with the recognition of close relatives, but Hamilton also thought that if the dispersal of individuals is limited, this might build up enough local genetic similarity to favour a less targeted kind of altruism towards neighbours in general. Because local dispersal is very common, this mechanism might greatly expand the range of cooperation in nature. However, later models suggest that this is not necessarily so: when limited dispersal makes neighbours close relatives, it also makes them close competitors, and this can negate the effect of kinship. On page 1024 of this issue. Griffin and colleagues provide the first experimental test of this effect, confirming that both kinship and the scale of competition matter.