A new study published in the journal, Science, shows that it’s okay to have children with first cousins despite being related. Scientists delved even further and revealed when people stopped marrying their cousins as well as the genetic effects of having children with cousins.
According to the study, people would, on average marry their fourth cousins between 1650 and 1850. The century that followed saw people change their marriage habits due to technological changes and the growth of cities. By 1950 people would marry, on average, their seventh cousins.
Researchers explained that changes in transportation allowed people to travel further to look for a partner, extending accessibility. Before the first half of the twentieth-century people were more inclined to look for a spouse within a six-mile radius of where they were born and established a family in the same area.
Among the factors that continued to erode this habit included shifting social norms, shrinking family size, and the increasing autonomy of women. All these changes resulted in cousin marriage becoming a taboo, even if it was considered an efficient way of keeping money in the family.
In addition, states began to outlaw marriage between cousins after the end of the Civil War.
According to the study, people who are first cousins share 12.5 percent of their DNA. This figure drops the further away the relation is to the person.
Researchers revealed that children between first cousins have a 4 to 7 percent chance of being born with birth defects. People who are more distantly related have a 3 to 4 chance for their children to be born with birth defects. In other words, sharing a number of genes is not advised as it can lead to a number of genetic diseases.
While the figures are low enough for many people to take the chance, the problem is if the child wishes to reproduce with their first cousin. According to the study, offspring resulting from such unions would have a great deal of genetic material in common, thus increasing the chance of birth defects.
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