When speakers of different languages meet, their words, sounds and even grammatical structures mingle in surprising ways. 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. Nevertheless, the new study found unexpectedly high levels of borrowability for certain aspects of grammar, such as past tense (which not all languages have). “We can use this kind of idea to reveal connections between languages and cultures that we didn’t know existed,” Greenhill says.