| Inbreeding is no more harmful than outbreeding unless inbreeding is practiced erratically in an otherwise outbreeding population. In outbreeding populations, mates are less likely to share close ancestry and thus the same harmful recessives traits. In this kind of reproductive system, recessive genes do not wash out of the population and thus accumulate as a large genetic load. The result can be the manifestation of harmful characteristics in the offspring of mating relatives.
For most of human history, breeding populations were small and isolated, and the community often practiced cousin marriage. The results were a relatively homogenous population of inbred individuals. Such homogenous populations are also common in other species . It is unlikely, therefore, that a naturally selected mechanism would evolve to prevent incest/inbreeding. |