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Darwin's wife, Emma, was his first cousin, and he was concerned about the impact of inbreeding on his ten children, three of whom died at age ten or younger; three others had childless long-term marriages. [16] [17] [18] Humans do not seek to completely minimize inbreeding, but rather to maintain an optimal amount of inbreeding vs. outbreeding.
Inbreeding coefficients of various populations in Europe and Asia. Offspring of biologically related persons are subject to the possible effects of inbreeding, such as congenital birth defects. The chances of such disorders are increased when the biological parents are more closely related.
Inbreeding can lead to inbreeding depression within the population, and this can cause fewer offspring, more birth defects, more individuals prone to disease, decreased survival and reproduction (fitness), and decreased genetic diversity within the population.
Genetic purging is the increased pressure of natural selection against deleterious alleles prompted by inbreeding. [1]Purging occurs because deleterious alleles tend to be recessive, which means that they only express all their harmful effects when they are present in the two copies of the individual (i.e., in homozygosis).
Birth defects are divided into two main types: structural disorders in which problems are seen with the shape of a body part and functional disorders in which problems exist with how a body part works. [3] Functional disorders include metabolic and degenerative disorders. [3] Some birth defects include both structural and functional disorders. [3]
Inbreeding avoidance, or the inbreeding avoidance hypothesis, is a concept in evolutionary biology that refers to the prevention of the deleterious effects of inbreeding. Animals only rarely exhibit inbreeding avoidance. [ 1 ]
Suicidology is the scientific study of suicidal behaviour, the causes of suicidalness and suicide prevention. [1] Every year, about one million people die by suicide, which is a mortality rate of sixteen per 100,000 or one death every forty seconds. [2]
Most of the gene defects are autosomal recessives, so that if both the mother and father carry the same defect, the chance that their child will have the associated disease is 1 in 4. The molecular genetics of many of these diseases have been determined, enabling genetic testing , prenatal testing , and counseling.