Tendon-associated bone features of the masticatory system in Neandertals

Abstract

Masticatory or paramasticatory activities are often considered to have produced elevated stresses important in the evolution of the Neandertal face. Yet Neandertals were geometrically ill-equipped to produce absolutely great anterior bite forces due to their relatively long bite-force lever arms. To consider whether Neandertals might have had structurally different masticatory muscles capable of producing more force than modern human muscles, this study examines the form and frequency of bone features known to be associated with internal tendons (structure) of the masticatory musculature in four species of macaques (n=85), three geographically distinct samples of modern humans (n=111), and Neandertals (n=27). Neandertals present a mosaic of tendon-associated bone features compared with macaques and humans. The Neandertal deep masseter and anterior temporalis are inferred to be better defined and perhaps larger than in modern humans based on their better developed deep masseter fossae and presence of a postorbital ridge. Medial pterygoid bone features were not qualitatively different from those in some modern humans although the medial pterygoid tubercle is larger, on average, in Neandertals. These results imply the presence of moderately stronger masticatory muscles in Neandertals than in modern humans. A moderate increase in masticatory muscle strength is considered necessary in Neandertals to offset their relatively prognathic face. However, the differences are small enough that it remains unlikely that Neandertals could produce absolutely great anterior bite forces.