Social scientists are well aware of the consequences of what’s called assortative mating, that is, the fact that marriages tend to occur between people who are similar in things such as interests, social status, education and wealth. Biologists, on the other hand, have tended to ignore it. “When studying the genetic underpinnings of correlated traits, “for mathematical convenience, we’ve assumed basically for forever that mating is random,” Richard Border told BioWorld. “Which it isn’t.”