Darwin has given us a background about how beneficial traits shape up in natural populations, but one is led to wonder about the manner of development of costly traits. Two theories have tried to address this challenge - the theory of hitch hiking and theory of kin selection.
The theory of hitchhiking has indicated that genes which present a cost to their bearer can become frequent in natural populations when they "hitch a ride" with healthier genes that are being preferred by natural selection. On the contrary, the theory of kin selection indicates that costly traits are preferred, if they result in gains for relatives of the bearer, who also carry the gene.
"Animal traits are not always independent. For example, people with blond hair are more likely to have blue eyes," explains Andy Gardner (Oxford University). "This is a nuisance for natural selection, which could not, for instance, favor blond hair without also indirectly favoring blue eyes, and this is the idea of genetic hitchhiking."
Kin selection is similar, but here the genetic associations are between different individuals: "If I have a gene that makes me more altruistic, then I can also expect my relatives to carry it. So while the immediate effect of the gene is costly for me, I would benefit by receiving altruism from my relatives, and so the gene is ultimately favored," Gardner explains.
New research carried out at the University of Edinburgh and Queen's University, Canada shows that both processes are governed by the same equations. This reveals that kin selection can be seen as a special form of genetic hitchhiking, explain Gardner and his coauthors Stuart West and Nick Barton (University of Edinburgh) in the February issue of The American Naturalist.
The researchers built on a general framework for modeling hitchhiking first proposed by Barton and colleagues, showing how it can be used to describe social evolution and recovering the classical results of kin selection theory. This insight raises the possibility of using the tools of hitchhiking theory to explore social problems that have so far been too complicated to analyze using traditional kin selection technique.