Differences in masticatory loads impact facial bone surface remodeling in an archaeological sample of South American individuals

Abstract

The reduction of masticatory strains is considered one of the main factors that led to a pronounced morphological variation of the facial skeleton among modern humans. Although the archaeological record has provided evidence of bone remodeling activity being linked to craniofacial variation, its link with subsistence strategies has been proposed but not yet tested. Here, we evaluate the relationship between the strains arising from masticatory loads in the facial bones and the observed surface bone remodeling activity in adults and subadults from archaeological sites from South America that exerted different masticatory loads during life. We simulated the impact of mechanical loading during I1 and M1 bite using finite element analysis in six skulls from two archaeological samples, one of hunter-gatherers from Patagonia and the other of horticulturists from Northwest Argentina. The extension and distribution of bone formation and resorption were registered by a periosteal bone surface analysis on facial bones. We found a similar spatial distribution of high and low strains between samples and across ages, but different magnitudes. In general, compression strains corresponded with resorption activity, while tension strains corresponded with formation activity. Our results show a relationship between mechanical bone response to masticatory loading and bone remodeling activity, which can ultimately shape cranial morphology. We propose that although there are differences in skull morphology among populations that are established early in ontogeny, mechanical loading produced during mastication can enhance such differences. These results then support the idea that craniofacial morphology can contribute to reconstructing the history of past populations.