Indigenous people entered North America at least four times between 12,000 and 24,000 years ago, bringing their languages with them, a new linguistic model indicates. The model correlates with archaeological, climatological and genetic data, supporting the idea that populations in early North America were dynamic and diverse.

Nearly half of the world’s language families are found in the Americas. Although many of them are now thought extinct, historical linguistics analysis can survey and compare living languages and trace them back in time to better understand the groups that first populated the continent.

In a study published March 30 in the American Journal of Biological Anthropology, Johanna Nichols, a historical linguist at the University of California Berkeley, analyzed structural features of 60 languages from across the U.S. and Canada, which revealed they come from two main language groups that entered North America in at least four distinct waves.