Inbreeding in humans is the process of mating genetically similar organisms, which can lead to the production of offspring with homozygosity of recessive alleles. In humans, inbreeding is associated with consanguinity and incest, in which close relatives mate. The effects of inbreeding can be deleterious, and it goes against the biological aim of mating, which is the shuffling of DNA. Inbreeding can lead to a higher probability of both alleles in one locus being derived from the same allele in an ancestor, which is called the "coefficient of inbreeding". Some of the effects of inbreeding in humans include:
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Impairment of function: Inbreeding has been shown to be associated with impairment of function because of homozygosity of recessive alleles, which occurs across a wide range of traits and suggests a large number of deleterious alleles in the human genome.
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Increased childhood mortality: Reports on the health effects of inbreeding have focused mainly on its impact on reproduction, childhood mortality, and rare Mendelian disorders. For example, a 4–5% increase in childhood mortality has been found in the offspring of first cousin marriages, and similar results have been reported in other species.
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Late onset disorders: The effects of inbreeding on late onset disorders are largely unknown, despite the fact that deleterious effects of inbreeding in other species are known to increase with age.
Inbreeding is a technique used in selective breeding, such as in livestock breeding, where breeders may use inbreeding when trying to establish a new and desirable trait in the stock and for producing distinct families within a breed.
