A British study recently looked at how the transition fromhunter-gatherer to farmer among humans some 10,000 years ago led tomodification of the shape of the lower jaw that today means more peoplevisiting the orthodontist. Noreen von Cramon-Taubel, an anthropologistat the University of Kent, found that the resulting diet shift to softerfoods 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 farmingand five hunter-gatherers—from Africa, Asia, Australia, Europe, and theAmericas.

Measuring the shapes of 322 crania and 295 jaws from museums,Cramon-Taubel (pictured) found a significant correlation between jaw shape andmeans of living. While hunter-gatherers tended to have longer andnarrower lower jaws, farmers had shorter and wider jaws. The craniaexamined did not show a similar correlation, however, Cramon-Taubel didnote that the palate shape of the upper jaw—which is closely associatedwith the lower jaw and is involved with chewing—also varied betweenfarmer and hunter-gatherers.

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

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