Starting from the generation of the common ancestor, the common ancestor is the first generation, and if there is intermarriage within the third generation, it belongs to consanguineous marriage. If cousins get married, their maternal grandmother is the first generation, their mother is the second generation, and the combination of cousins is the third generation.
The harm of consanguineous marriage
1. Marriage between close relatives can greatly increase the probability of recessive genetic diseases. According to relevant data, the incidence of recessive genetic diseases in offspring of consanguineous marriages is 150 times higher than that in offspring of non consanguineous marriages.
2. The incidence rate of some polygenic genetic diseases in close marriage is higher than that in non close marriage. According to the survey, the incidence rate of polygenic diseases such as congenital heart disease, anencephaly, spinal cord fission and so on in the offspring of close relatives married is about 1.64%, higher than 0.57% in the children of non close relatives married.
3. Children who marry close relatives also have higher early mortality and deformity rates.
4. The offspring of consanguineous marriage will have poorer physical fitness, lighter weight, and shorter height.