Interesting news item from National Public Radio: Birds of a feather flock together. The age-old adage now carries scientific weight. A new study in the Proceedings of the National Academy of Sciences suggests genes may influence how people pick their friends. James Fowler, professor of medical genetics and political science at the University of California, San Diego, is the author of the study and he tells host Guy Raz there’s biology in social chemistry. Read or listen more here.