When speakers of different languages meet, their words, sounds and even grammatical structures mingle in surprising ways. Ketchup, for example, may be an American staple today, but its name entered English via the Chinese language Hokkien around the end of the 17th century. Or consider the phrase “attorney general”: we place the adjective after the noun because that was standard word order in French when the Normans invaded England in 1066. This kind of exchange, called linguistic “borrowing,” is a big part of how languages evolve worldwide.
Because of gaps in the historical record of human encounters, it can be hard to measure exactly how contact between different populations shaped any given language over the years. But a vestige of all those past interactions persists in human DNA: whenever a person’s genes indicate their ancestors came from two separate populations, it stands to reason that said ancestors interacted closely enough for their languages to merge, too. So a team of researchers analyzed genetic data from nearly 5,000 individuals living in the last few decades, spanning every inhabited continent, and identified 126 cases where those individuals’ ancestry indicated interbreeding between two distinct populations at some point in the past. Though a person’s genetic heritage doesn’t necessarily reflect the language they speak, the researchers expected to find similarities between the languages spoken by those converging groups.
