Inbreeding avoidance in animals.

The phenomenon of inbreeding depression is well documented and behavioral adaptations for inbreeding avoidance have been described. However, there is debate over whether inbreeding depression is always an important selective force on behavior. Here, we summarize recent evidence for inbreeding depression under natural conditions, review inbreeding avoidance mechanisms, and discuss how these are influenced by social structure. We also examine the idea that animals have evolved mechanisms to avoid outbreeding.