A British study recently looked at how the transition from hunter-gatherer to farmer among humans some 10,000 years ago led to modification of the shape of the lower jaw that today means more people visiting the orthodontist. Noreen von Cramon-Taubel, an anthropologist at the University of Kent, found that the resulting diet shift to softer foods that required less chewing led to a shortening of the human jaw, which has made crowding of teeth an issue for modern humans.

The study looked at skull and jaw shape in 11 populations—six farming and five hunter-gatherers—from Africa, Asia, Australia, Europe, and the Americas.

Measuring the shapes of 322 crania and 295 jaws from museums, Cramon-Taubel found a significant correlation between jaw shape and means of living. While hunter-gatherers tended to have longer and narrower lower jaws, farmers had shorter and wider jaws. The crania examined did not show a similar correlation, however, Cramon-Taubel did note that the palate shape of the upper jaw—which is closely associated with the lower jaw and is involved with chewing—also varied between farmer and hunter-gatherers.

Cramon-Taubel looked at whether other factors, including geographic location, genetic history, and climate variation, could account for the difference in jaw shape between the two groups, but found no evidence. Instead, she concluded that the transition to farming, which increased food processing and consumption of easier to chew food, changed the shape of the human jaw. This shortening, she contends, resulted in greater dental crowding and the need for more orthodontics.

The findings appear in the Proceedings of the National Academy of Sciences.