image: Biomechanical modeling shows that labiodental sounds like "f" are easier to produce (and to accidentally arise) under overbite and overjet (A) than under the edge-to-edge bite (B) that prevailed before the Neolithic (C). Overbite and overjet persisted only when exposed to the softer diets that became characteristic with food production (D versus E) and more recently with intensified food processing (F). Both developments led to a spread of labiodental sounds.
Labiodental sounds, such as F and V, have been known to be rarely met in hunter-gatherer languages. To understand how this has occurred, the authors undertook a massive statistical inquiry. 2,400 languages were analyzed, and a biomechanical model of mouth and lip movements was created.
The following explanation was put forth - when transition from hunter-gatherer society to agriculture and animal husbandry happens, diets also undergo major changes; specifically, foods become softer. This leads to changes in bite configuration and thus facilitates easier pronunciation of labiodentals.