Society, Genetics, and the Impact of Consanguineous Marriages: At the Intersection of Education and Heredity

Many immigrant groups in Europe are known for having a high occurrence of consanguineous marriages, or incestuous unions. The issue with this can be summarized as follows: children born to closely related parents have a lower degree of heterozygosity because a significant portion of their genes comes from the same individual—for example, from a grandparent in the case of cousins. In other words, these individuals inherit identical gene variants more frequently than others.

As a result, genes that usually appear in humans as a single copy without affecting their outward characteristics, or phenotype, become visible. Among these genes, there are often many defective variants in one way or another.

The rarity of these recessive genetic defects is due to natural selection, which works against them. It operates in such a way that individuals with an observable genetic defect tend to have fewer offspring than others. Consequently, their genes do not pass on to future generations as effectively as those of other individuals.

It’s important to note that recessive genetic defects are not always clearly visible diseases. Often, they are only mildly harmful and thus primarily affect an individual’s vitality—for example, by impairing physical or mental performance—and are not considered outright diseases.

Since recessive gene variants only affect people when inherited from both parents, children born from consanguineous marriages are more likely to have disabilities. Even the seemingly healthy offspring of such unions tend to have, on average, fewer abilities than other people.

This is likely one of the most significant reasons why certain immigrant groups have struggled to succeed in Western societies, and it strongly influences the poor learning abilities observed in their children.

For this reason, consanguineous marriages should not be a taboo or off-limits topic in an increasingly diverse society but, rather, the opposite. And because this is a growing issue, the public—especially those from cultures that favor consanguinity—must be educated on the negative consequences of this tradition.

In other words, incestuous unions and their harmful societal effects must be openly discussed!

This should also be addressed—especially in schools—even if some students are themselves the offspring of cousin marriages. It is essential for them to understand this issue, break the harmful tradition of their culture, and choose spouses from outside their family.

It’s worth emphasizing that the hereditary harms caused by consanguineous marriage disappear entirely within a single generation. Therefore, even the descendants of the most inbred members of the most incestuous cultures are not doomed to the bottom of society—provided they understand the importance of not procreating with a relative.

Previous thoughts on the same topic:
Finnish Society Adopts Medieval Characteristics
Freudian slip, 9-year-old girl and cultural appropriation
Cousin is not just a delicacy, but also a hindrance to social success

Cousin is a cultural delicacy

We Europeans are well aware that among many developing nations, it is common to marry relatives. So the idea is, "the cousinier, the juicier."

What remains unclear, however, is whether this has been the original behavior of humanity or a later cultural development, despite some indications suggesting an increase in consanguineous marriages among humans in recent times.

To get an answer, one must of course examine human groups that lived long ago. And it was precisely such a research report that I recently came across.

The study I read analyzed the last hunter-gatherers inhabiting Western Europe, who soon became displaced by the farming newcomers spreading from the southeast of the continent - or merged with them. The examined individuals had inhabited southern Brittany in France approximately seven or eight thousand years ago.

The analysis of ten individuals from three different locations revealed that spouses were not sought from within their own groups but from among different groups residing in different locations. As a result, consanguineous marriages were avoided, despite the very small population of each group - and consequently, also of the hunter-gatherers living in the area.

Somewhat surprisingly, researchers also found that the hunter-gatherers did not seek spouses from farming communities, even though such communities existed in the vicinity. Thus, the hunter-gatherer communities of the time remained quite separate for a long time, even though there was migration from them to the farming communities.

Returning to the question of cousin marriages that initiated this blogpost, based on the study I've discussed, it can be concluded that the original inhabitants of Europe did not practice such marriages.

In other words, they had an excellent understanding that marrying cousins was not sensible. This seems to be not clear to all contemporary human groups, those who, for one reason or another, have adopted consanguineous reproduction in their culture.

Previous thoughts on the same topic:
Violent demographic changes in Denmark
History of Finland I: How did Finland become culturally part of the West?
Long distance trade