DNA Misconceptions
Carl Zimmer’s article “Seven Big Misconceptions about Heredity” (May/June 2019) makes some excellent points, and I would like to amplify a bit on “Misconception 1: Finding a Special Ancestor Makes You Special.” Using the generally accepted rule of thumb that there are three generations per century, it is possible to estimate how many ancestors a person has at a certain historical time. Because we all have two biological parents, the number of ancestors is simply two taken to the power given by the number of generations. For example, two hundred years ago would be six generations back, and the number of ancestors would be two to the sixth power, or sixty-four.