Fans of classic movies will remember the famous dueling banjos scene in Deliverance, the story of four city friends who take an ill-fated boating trip down a backwoods Georgia river. As the friends set out, one of the friends challenges a local boy with a banjo to see who can play faster. At the end of the song, the camera zooms in to reveal the boy’s diseased, inbred features.
Such images have contributed to the taboo against marriage between first cousins. Geneticists explain that since closely related persons are more likely to harbor identical genetic mutations, their children have a greater chance of being born with defects.