“Evolution of inbreeding avoidance and inbreeding preference through mate choice among interacting relatives”

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A. Bradley Duthie and Jane M. Reid

Evolution of inbreeding strategies may be much more restricted than is commonly presumed

Should individuals tolerate incest?

A new study has revealed that tolerance of incest might be more likely than previously assumed. Incestuous mating is taboo across many human cultures, but many animal species engage in incestuous mating (inbreeding). When animals inbreed, their inbred offspring are typically less likely to survive than would be expected if they were instead outbred offspring.

Because of the decreased survival of inbred offspring, it is widely presumed that animals will evolve to avoid inbreeding. However, because relatives also share genetic material, individuals that inbreed can potentially benefit evolutionarily by passing more copies of their genes to subsequent generations, if the costs of decreased offspring survival is sufficiently weak. Therefore, populations might sometimes evolve in which individuals tolerate or even prefer incestuous mating.

Duthie and Reid use computer simulations to model the evolution of inbreeding behavior in populations over multiple generations. They thereby model both the complexity that affects mating interactions among relatives, and the emerging family history upon which such interactions depend. Duthie and Reid find that inbreeding avoidance typically evolves when inbreeding depression is moderate to severe, and that inbreeding preference evolves only when inbreeding depression is negligible. The evolution of inbreeding avoidance and inbreeding preference are also both highly constrained if avoiding or preferring inbreeding is costly, as might occur when such behavior requires active searching for acceptable mates. Further, evolution of either inbreeding avoidance or inbreeding preference is also highly constrained if individuals can only identify siblings, and not more distant relatives.

These results shed new light on the evolution of behavior surrounding incest, and show that the conditions under which incest avoidance evolves are likely to be more constrained than previously believed. Read the Article