Variation in facial bone growth remodeling in prehistoric populations from southern South America

To assess the intraspecific variation in bone remodeling patterns in modern humans, we studied two populations from southern South America that represent the extremes of morphological variation in this region. We particularly analyzed the ontogenetic changes in the patterns of bone growth remodeling and compared the patterns between samples.

We obtained high-resolution casts of the periosteal surface of the upper and middle face of subadults (n = 36) and adult (n = 36) individuals from a sample of hunter-gatherers from Patagonia and a sample of horticulturists from Northwest Argentina. The areas of bone formation and resorption were registered using an incident-light microscope. We then estimated the average bone remodeling map by sample and age, and performed principal component analysis and multivariate regressions to assess the extension and distribution of these areas across ontogeny and between samples.

We found that the remodeling pattern of the glabella, supraorbital arch, frontal process of the maxilla, and a large part of the zygomatic bone is relatively constant in subadults and adults from both sample with a clear predominance of bone formation. In contrast, the middle face is characterized by the spatial alternation between formation and resorption areas, and greater variation with age and between samples. The main differences were found in areas related to chewing and muscle insertions.

Our study provides the first evidence of interpopulation variation in bone growth remodeling and suggests that biomechanical factors can influence the observed patterns. It also underlines the need to account for ecological factors in within and between species comparisons.