Everyone may have a common illusion that the ancient laws of our country did not prohibit the marriage of close relatives, but in fact, the laws of most dynasties stipulated that close relatives could not get married. For example, it is recorded in Shu Wei: "Xia Yin does not doubt the marriage of a family, and the marriage of the same surname was not allowed until the Zhou Dynasty." Marriage between people with the same surname was not allowed in the Zhou Dynasty. Later, the Qing dynasty made more detailed regulations, but these regulations were not binding on the people, especially in the Ming and Qing dynasties, when consanguineous marriage was very common.

The current marriage law in China does not allow consanguineous marriage. The main reason is not only social ethics, but also genetic problems that may arise from inbreeding. What is a close relative? According to the marriage law of our country, relatives who are related by blood within three generations are called close relatives, and men and women within this range cannot get married. But in ancient times, consanguineous marriage was very common. For example, in A Dream of Red Mansions, Lin Daiyu's mother and Jia Baoyu's father are brothers and sisters, and Jia Baoyu and Lin Daiyu are close relatives. Xue Baochai's mother and Jia Baoyu's mother are sisters, and Jia Baoyu and Xue Baochai are also close relatives, but they finally got married.

▲ "Dream of Red Mansions" stills

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So why did the ancients intermarry? This is related to the clan system in feudal society. The so-called pro-family relationship is to stabilize family power through marriage. Moreover, women in ancient big families rarely go out, and they all meet cousins, and both families know each other better. Therefore, in ancient times, many large families would choose close relatives to marry, but generally they would not marry with the same surname, that is, cousins did not often marry.

Inbreeding was very common in ancient times. For example, Lu You and his wife Tang Wan are cousins, and their relationship is very good. But because Lu You's mother didn't like Tang Wan, they finally had to break up. Lu You also wrote a sentence in "Hairpin Phoenix": "Although there is a mountain alliance, it is hard to believe the brocade book", which shows his sadness.

▲ Lu You, Tang Wan stills

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Chen Ajiao, who was married by Emperor Wu of the Han Dynasty, was also his cousin. In addition to brother and sister, there are many examples of intergenerational marriage in ancient times. For example, princess Chen, her daughter, married her uncle; Yang, the nephew of Emperor Xuanzong of Tang Dynasty, said that he married Princess Weiguo, the daughter of Emperor Xuanzong of Tang Dynasty.

However, you may find that although consanguineous marriage was very common in ancient times, there are few records about children born after consanguineous marriage having intellectual or other genetic problems. Experts say, let's take a closer look at the details first. Generally speaking, the offspring of consanguineous marriage are much more likely to have mental deformity and disability defects than the offspring of normal marriage. There were several reasons why so many close relatives got married in ancient times, but not many.

▲ Ancient wedding stills

First, close relatives of ancient people usually got married between first-degree cousins. In such a genetic relationship, the similarity of genes is not particularly great. Therefore, the probability of obvious defects in their offspring is relatively low, probably less than 1/4. The families of the ancients generally had many children, and four or five were very small, so the probability of defects in such data was even lower. Moreover, according to the scientific and medical conditions at that time, children with congenital defects rarely survive smoothly, so they naturally will not pass on the defective genes to the next generation.

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Second, polygamy was practiced in ancient times, especially in some large families. Therefore, the relationship between relatives is more complicated, even cousins contain multiple layers of intermediate relationships. On the contrary, most blood relations are distant relatives, and many are only nominal close relatives. As far as blood relationship is concerned, it is not within three generations.

▲ Cousins in film and television dramas

Third, due to the economic situation and social structure, families in feudal times had a low burden on the disabled and there were no restrictions on having children. Therefore, many families will kill newborns once they find that they are born with disabilities or mental problems. This also happens to a large number of baby girls. Many baby girls were abandoned or drowned at birth because of the serious preference for sons over daughters in feudal times. In this case, the government will not ask.

Fourth, the infant mortality rate in ancient times was quite high. Due to the limitation of scientific and technological level and living conditions, the life expectancy of ancient people is generally not long. In ancient China, the average life expectancy was about 30 to 40 years, including a large number of premature babies. In ancient times, women generally married early, and having children was like passing through the gates of hell, not to mention weak newborns.

▲ Ancient baby stills

Even if it is not the offspring of inbreeding, it is easy to die, and almost every family has children who die. If there are physical defects due to inbreeding, such a baby will be more difficult to survive.

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In fact, it is also possible for close relatives to get married and give birth to defective offspring. It does not mean that after close relatives get married, the offspring will be defective. Only in modern society, since we know the disadvantages of consanguineous marriage, we must avoid it. Coupled with the social and ethical problems caused by consanguineous marriage, most countries prohibit consanguineous marriage.