Inbreeding is not good. European royal families know this well. That is why the horizon that dating apps like Tinder open to meet people outside of our circles is so important. However, despite attempts to find partners as far away as possible from one’s own family; 1 in 10 marriages that take place are between first cousins or second cousins. Marrying cousins, according to a new study, is much more common today than in prehistoric times. But let’s go by parts: why shouldn’t we marry cousins? And what does this research say about having children among direct relatives?
Royal families, like the Romanovs, know well what inbreeding produces. Marrying between first or second cousins can bring to the surface many genetic diseases, such as hemophilia. But there are other X-linked disorders or consanguineous diseases that appear with inbreeding. Although those who had it worst were the pharaohs, who married brothers.
For all these diseases and disorders, due to the current way of relating to us, it does not make sense that we continue to look for our better half near our family circles. In fact, thanks to the new study, published in the scientific journal Nature Communications, we now know that not even in prehistory first cousins or second cousins reproduced among them. In fact, it was much less typical than we have thought (or fiction has led us to believe), as explained by IFL Science.
Inbreeding: more now than in prehistory
Of the remains of 1,785 people, only 53 were the result of a relationship between cousins and one, an incestuous relationship. But today 1 in 10 marriages are between first cousins or second
The researchers in this study have examined the remains of 1,785 people that lived between 45,000 years ago and until just a few hundred years ago. Of all these, just 53, that is, 3% of them have DNA that indicates that his parents were cousins brothers. What’s more, one of them resulted likely to be the fruit of a incestuous relationship between siblings or parents and children. In addition, it should be noted that these 53 people were not born in the same place or at similar times, which could be an explanation since clans were sometimes isolated from each other. Ultimately, these people who had parents who were cousins were distributed without rhyme or reason through history and the continents.
Although it is true that sometimes parents may be more distantly related. This, known as “background kinship,” has also been investigated by the study authors and realized that it was much more common before agriculture came along. “Parents can also be more distantly related to each other, often through many deeper connections in their pedigree, as a common consequence of small population sizes, or as a consequence of founding effects in tightly knit groups.”
And is that the agricultural activity the population increased and, therefore, it was easier for there to be more genetic variability. So there was a drastic decline in background kinship and it started to be much less common.
DNA analysis, key to knowing if the parents were cousins
And how has this study been done? To find out if the remains of people who have undergone genetic analysis were fruit of parents related to each other, the DNA is searched for stretches with little genetic variation. These stretches are known as “regions of homozygosity” or ROH. “The more recent the genealogical relationship of the two parents, the more frequent and long the resulting ROH tends to be,” the authors write. Ultimately, the key to knowing if they were cousins was in the DNA study of these remains.
Therefore, this widespread belief that in prehistoric times people married cousins we now know that it is not true. Inbreeding was not a situation that occurred regularly. What’s more, more first or second cousins are getting married now than before. And that we have tools like Tinder that allow us to get as far as possible from our family tree.