In today's world, China is the only country or region that explicitly prohibits cousins from getting married, and other countries do not prohibit cousins from getting married. 200 1 a scientific report published by an authoritative magazine in Australia said that the probability of a cousin getting married and giving birth to a mentally retarded child is three times that of a non-relative getting married and giving birth to a sick child. However, Allen Bito, a professor of comparative genomics at Murdoch University, has found that most of the children born to cousins are healthy through 30 years of continuous research, and the previous conclusions are not valid.
In ancient China, "consanguineous marriage" was only between cousins, and the genetic similarity was not very great, so the probability of giving birth to a child with obvious birth defects was less than a quarter. In other words, those cousins who have five or six children may only have one mental retardation, and the other children are healthy. According to the social and medical conditions at that time, it was difficult for such mentally retarded children to live beyond adulthood, and most of them died of congenital diseases at a very young age, and they would not pass on the sick genes to the next generation.
Everyone has seen the Dragon Eight Branches. Wang Yuyan wanted to marry her cousin Mu Rongfu from the beginning. Fortunately, the little prince Duan Yu appeared in time. Although everyone thought that Wang Yuyan was his own sister, in the end, the plot reversed and Duan Yu became Duan Yanqing's child. However, even if Duan Yu and Wang Yuyan don't want brothers and sisters, they are collateral blood relatives within three generations, and there is a chance to give birth to mentally retarded children in genetic probability. But there is no more explanation in the book, so I can't say more.
2 1 At the beginning of the 20th century, through the investigation conducted by Professor Bito in 1 1 country, it was found that the probability that unrelated couples gave birth to deformed babies was 2%, while the probability that close relatives gave birth to deformed babies only increased to 4%. In addition, the infant mortality rate of close relatives is only 1%, while the probability of a cousin getting married and giving birth to a deformed baby is less than 3%. It is related to the probability that excessive drinking and smoking will eventually cause offspring with mental retardation. It can be seen that personal living habits are still very important.
Finally, we all know Einstein, Darwin and Jerry Lee Lewis are married cousins, but this behavior is only a common phenomenon in some countries. However, we don't advocate consanguineous marriage, but only dispel the concerns of couples about this kind of thing and avoid the tragedy caused by the breakup of couples.