In ancient times, many cousins married cousins, why did they rarely give birth to mentally handicapped children? In fact, the reason is very simple!
Why didn't an ancient cousin marry a cousin have a deformed child? In film and television dramas, it is often seen that cousins become relatives, cousins marry cousins, and cousins marry cousins. According to modern science, the marriage of cousins and brothers is already considered to be the marriage of close relatives, so why were there not many mentally retarded children born in ancient times? Why?
In ancient times, although it was very liked to marry close relatives, it was generally between cousins and sisters. Marriage between cousins and sisters is strictly forbidden, which shows that in ancient times, it was also known that marriage between close relatives would be detrimental to future generations. They all believe that the children are passed down from father to father, and that only people with the same surname will be considered to be in the family, so marriage is forbidden. Cousins generally have different surnames, so in ancient times they were allowed to marry, but in ancient times such marriages were generally for the purpose of expanding power or political marriages.
In ancient times, there were indeed many close relatives who married, such as Lü Hou, in order to consolidate the imperial power, let his granddaughter and son marry, but later Liu Ying did not marry Lü Hou's granddaughter. The poet Lu You, whom we learned in elementary school, has a relationship with his cousin! In the famous Dream of the Red Chamber, Jia Baoyu and Lin Daiyu and Xue Baochao are all related by blood!
So in ancient times, since so many close relatives married, why were not many mentally retarded children born? Are there any reasons for this?
The first point: the more you have, the less chance
What the ancients called "consanguineous marriage" was only between cousins (first-order cousins, the same below), so the genetic similarity was not particularly large, so the probability of having a child with obvious observable genetic defects was about a quarter. In ancient times, there were also five or six children, and only one of the problematic children such as mentally retarded children may appear. Moreover, the social medical conditions at that time, it was difficult for such children to live past adulthood, so many children, one bad would not think too much.
Second point: polygamy, complex kinship
In ancient times, polygamy, and most of them are extensions of the family or the collateral of large families, those so-called cousins are actually not known how many turns and how many layers of blood relations are separated, so most of them are not married within three generations in the pure sense.
The third point: it is cleaned up when it is born
In ancient times, the concept of clans was strong, and some families still had clan rules, and the government could not interfere. It is permissible for the clan to execute women who have lost their private virtues and children who are born inadequate. Therefore, if a child is born with insufficient congenital deficiencies, there are not a few who drown or strangle them.
Point Four: Miscarriage
Another important reason is that it is impossible to be born, and the ancient living standards and medical standards are far lower than the present. Originally, there were many deficiencies in children after the marriage of close relatives, and in ancient times, pregnant women miscarriages also often occurred, and children who were born with insufficient children may not live long in the stomach as early as possible.