The geneticist Jim Wilson, at the University of Edinburgh, was shocked by the frequency he found in the U.K. Biobank, an anonymized research database: One in 7,000 people, according to his unpublished analysis, was born to parents who were first-degree relatives—a brother and a sister or a parent and a child. “That’s way, way more than I think many people would ever imagine,” he told me. And this number is just a floor: It reflects only the cases that resulted in pregnancy, that did not end in miscarriage or abortion, and that led to the birth of a child who grew into an adult who volunteered for a research study.
Most of the people affected may never know about their parentage, but these days, many are stumbling into the truth after AncestryDNA and 23andMe tests.
It’s shocking to you that rape exists? Clearly its a bad thing and shouldn’t happen, and it’s upsetting, but I would disagree that most people would be shocked if you told them “more than zero rapes happened this year”.
While I agree with you in principle, I actually do think that 1/7k is unexpectedly high. If 1/10k people had an incestuous relationship, that would be low enough that I wouldn’t find it surprising. This study, if we take it to be cross-sectional, implies that the rate of incidence is much higher, at least on the order of 1/1k, possibly something around 1%. I don’t know the frequency that people of incestuous individuals have a child as a result, but the idea of it being higher than 1/7 strikes me as unlikely. Of course, multiple children can result from a pairing, so that has the potential to sway the numbers, but I’d hope that incestuous individuals are less likely to desire children from the relationship, and as a result would take a pregnancy as a sign to stop.