Inbreeding

Inbreeding is breeding between close relatives (called incest in the case of humans). If practised repeatedly, it leads to a reduction in genetic diversity. Inbreeding often leads to reduced health and fitness; however, livestock breeders often practice inbreeding, then cull unfit offspring, especially when they are trying to establish a new and desirable trait in their stock.

Inbreeding occurs in animals. For example, the cheetah is a highly inbred species, probably because of a population bottleneck in the species' recent past. Inbreeding is also deliberately induced in laboratory mice in order to guarantee a consistent and uniform animal model. Human genetic diversity is also extremely limited, again indicating a population bottleneck, some 100,000 years ago.