The functional significance of dental and mandibular reduction in Homo: A catarrhine perspective.

Veneziano, Alessio; Meloro, Carlo; Irish, Joel D.; De Groote, Isabelle; Stringer, Chris

The reduction in dental size and mandibular robusticity is regarded as a major trend in human evolution, traditionally considered the result of the peculiar extra‐oral food processing skills of Homo. The use of stone tools and fire would have allowed our ancestors to chew softer food in smaller bite size, thus relaxing the selective pressures to keep a large dentition and a robust lower jaw. This perspective assumes that differences in dental size and mandibular robusticity in hominins represent functional dissimilarities. This study uses a catarrhine comparative approach to test this fundamental assumption of the hypotheses on dental and mandibular reduction in Homo. A sample of extant catarrhines and fossil hominins was used to test for correlations between dental size, mandibular robusticity, and dietary proxies, the latter include diet quality, diet heterogeneity, feeding time, and microwear variables. The effects of phylogeny and body size were considered. Findings support the association between technological developments in Homo and reduction in incisor size and mandibular corpus robusticity, though not for premolar, molar size, and symphyseal robusticity. These results challenge the functional interpretation of postcanine reduction and symphyseal changes in the genus Homo. This work supports a multifactorial explanation for the reduction of the lower jaw in the genus Homo. The link between technological advancements in Homo and reduction in incisor size and mandibular robusticity is not rejected. Our analyses suggest using caution when interpreting the masticatory variability of non‐human catarrhines and fossil hominins. Reduction in tooth size and mandibular robusticity characterized the evolution of the genus Homo but the drivers for such trends have never been fully clarified. The study of catarrhine mandibular morphology offers the possibility to understand the constraints in which the masticatory apparatus of our ancestors may have evolved. In catarrhines, postcanine tooth size is dependent on body size and phylogenetic constraints, while incisor size and mandibular robusticity are associated to changes in diet quality and food mechanical properties. These findings suggest that extra‐oral food processing by the genus Homo may have played a role in incisor size and mandibular corpus reduction by assigning to the hands the job previously accomplished by the jaws.

COMPARATIVE method; HOMINIDS; HUMAN evolution; MANDIBLE; DIET

American Journal of Primatology, 2019, Vol 81, Issue 3, pN.PAG

0275-2565

Academic Journal

10.1002/ajp.22953