The influence of masticatory loading on craniofacial morphology: A test case across technological transitions in the Ohio valley

Abstract

Masticatory loading is one of the main environmental stimuli that generate craniofacial variation among recent humans. Experimental studies on a wide variety of mammals, including those with retrognathic postcanine teeth, predict that responses to masticatory loading will be greater in the occlusal plane, the inferior rostrum, and regions associated with the attachments of the temporalis and masseter muscles. Here we test these experimentally-derived predictions on an extinct human population from the middle and upper Ohio valley that underwent a marked shift from hunting-gathering to extensive farming during the last 3,000 years and for which we have good archaeological evidence about diet and food processing technology. Geometric morphometric methods were used to detect and measure the putative effect of diet changes on cranial shape independent of size. Our results partially confirm only some of the experimental predictions. The effect of softer and/or less tough diets on craniofacial shape seem to be concentrated in the relative reduction of the temporal fossa and in a displacement of the attachment of the temporal muscle. However, there were few differences in craniofacial shape in regions closer to the occlusal plane. These results highlight the utility of exploring specific localized morphological shifts using a hierarchical model of craniofacial integration.

Global human mandibular variation reflects differences in agricultural and hunter-gatherer subsistence strategies

“…Given the wider cultural changes associated with increased food processing and, therefore, consumption of a more homogeneous and softer diet in agriculturalists, it has been hypothesized that the dietary changes associated with agriculture are likely to have had an important effect on the form of the cranium and mandible (e.g., [3][4][5]. Although localized studies comparing hunter-gather and farming populations in Nubia (6), South America (7), the Ohio Valley (8), and the southern Levant (9) have found some support for an associated change between the masticatory apparatus and the initial transition to agriculture, it is currently unclear what effect agriculture has had on global patterns of human mandibular variation when compared against other wider microevolutionary factors, such as gene flow, migration, and natural selection. Hence, this study represents a global comparative analysis of the effects of subsistence strategy on modern human mandibular variation.…”

Sexual Dimorphism of North Indian Crania and its Forensic Application

“…Hard, tough and/or unprocessed diets generally lead to an increase in the overall robusticity or size of the skull, an increase in facial size, temporal muscle area, temporo-mandibular joint size and cranial vault thickness, wider and taller faces, thicker mandibles, and taller palates [33,34]. Lierberman.…”

The relative correspondence of cranial and genetic distances in papionin taxa and the impact of allometric adjustments

“…In humans, a number of studies have indicated that the morphology of the masticatory apparatus may be influenced by subsistence strategies (Larsen, 1997;González-José et al, 2005;Sardi et al, 2006;Lieberman, 2008;Pinhasi et al, 2008;Paschetta et al, 2010;Holmes and Ruff, 2011;Lieberman, 2011;von Cramon-Taubadel, 2011b). In particular, morphology of the mandible shows a weak correspondence with geographic distance (Nicholson and Harvati, 2006), and a lower correlation with neutral genetic distances than many other cranial regions (Smith, 2009).…”