For the John Templeton Foundation, I wrote about mapping a massive family tree.
One day in the summer of 1873 an English barrister opened the pages of the “Pall Mall Gazette” to leaf through the society wedding pages, noticed a union announced between two people with the same last name, and commenced wondering what the chances were that the couple were first cousins, as his own parents had been. So began one of the first endeavors in genetic genealogy, the attempt to reconstruct family trees en masse by analyzing sheaves of gathered data.
After two years of census-reading, fraction-computing, and deep dives into “Burke’s Landed Gentry”, George Darwin, the fourth son of cousins Charles Darwin and Emma Darwin, published his analysis. In “Marriages between First Cousins in England and their Effects,” the younger Darwin used the frequency of same-name marriages to estimate the national rates of cousin marriage by location and social class. Those in higher social classes, like the Darwins, seemed to marry their cousins at up to double the rate of the general population.