The paper, published Thursday in the journal Science, looks at genetic data from millions of online genealogy profiles. Among other things, the researchers were able to determine at what point in history marrying your cousin went out of vogue, and the average degree of relation between married couples today. And hey, since we’re on the subject: just how bad is it to have kids with your cousin?
While it’s taboo today, cousins used to get hitched all the time. Franklin Delano Roosevelt’s wife, Eleanor, was his fifth cousin once removed; she didn’t even have to change her name. And scientific geniuses like Albert Einstein and Charles Darwinmarried their cousins, too. For much of human history, these unions weren’t considered bad or gross. Oftentimes, there weren’t many better options.
From 1650 to 1850, a given person was, on average, fourth cousins with their spouse, according to Erlich’s data. “Many people may have married their first cousin and many people married someone not at all related to them,” he says. But within a century, that had changed. By 1950, married couples were, on average, more like seventh cousins, according to Erlich.
One common sense explanation for this shift is that when transportation methods improved, bachelors and bachelorettes had access to potential partners they had once been denied by geography. This makes sense, given that before 1950, most people stayed in place and ended up marrying someone who lived with in a six-mile radius of where they were born. Read more...