Marrying Your Cousin Is Not That Bad for Your Future Kids
Science & Tech / /
Marrying your cousin will not be the end of the family three, still scientists warn not to turn it into tradition.
Cousins getting married hasn’t always been a taboo. Back in the human history this marriages were not banned or considered bad, in many cases that used to be the only option.
From 1650 to 1850 people married, on average, their fourth cousin, according to Yabiv Erlich, a data scientist at Columbia University. “Many people may have married their first cousin and many people married someone not at all related to them,” he says. But there was noticeable change throughout time. In only a century married couples were, on average, seventh cousins, according to Erlich’s data.
An explanation that makes sense in this case is the mobility. As transportation methods improved people were able to access potential partners that were many miles away. This also explains why people before 1950 used to stay in place and ended up marrying someone who lived near to where they were born.
First cousins share 12.5% of their DNA. Therefore, any child from a first cousin marriage is likely to have a pretty substantial portion of similar-looking genes, which can be a problem.
As explained in Popular science article, genetic diversity is all the rage. If something goes wrong with the genetic material provided by the mother, the child is more likely to shake it off if father’s genetic material is very different, and vice-versa. If father’s left you hanging when it comes to susceptibility to a certain disease, a mother from a radically different gene pool could confer the protection you require. But when both parents are genetically similar, both versions of a gene are likely to shut down at the same time.
It’s estimated that 4-7% of children born in an union between first cousins are likely to have birth defects, compared to 3-4% for more distantly related parents. It’s not something that should be ignored, yet is not end of the world. The real issue is if this turns into a tradition. That case the offspring will have even more DNA in common—meaning a greater chance for birth defects.
In some nations with small populations, this is a serious issue. Iceland. for instance has, population of about 330,000 people concentrated mostly in the capital city, which makes many people worried they’ll accidentally marry a close relative. For that reason instead of using a conventional dating app they use Íslendinga-App, which warns if two people have too much genetic material in common.
Marrying your first cousin definitely carries some risk. But the possibility for healthy offspring improves as the relationship between parents is more distant, making their genes less similar. Second cousins share only 6.25% of their genes and third cousins share only 3%, while seventh cousins have no meaningful genetic relation at all.