Abstract
The transition to food production, exploitation of ‘secondary’ products (e.g., milk), and advances in cookware technology have affected all aspects of human life. The aim of the present study was to follow changes in mandibular form and shape throughout the terminal Pleistocene-Holocene Levant. The hemimandibles of four populations were included in this study: Natufian hunter-gatherers (n = 10), Pre-pottery Neolithic early farmers (n = 6), Chalcolithic farmers (n = 9), Roman-Byzantine (n = 16), and modern (n = 63) populations. A surface mesh of each mandible was reconstructed from CT or surface scans. Changes in mandibular form and shape were studied using the Procrustes-based geometric morphometrics method. Univariate and multivariate analyses were carried out to examine differences in size and shape between the studied populations. Our results reveal considerable temporal changes in mandibular shape throughout the Holocene Levant, mainly between the pre-agricultural population (the Natufian) and the succeeding ones, and between the post-industrial (the Modern) and the pre-industrial populations. A tendency for a reduction in mandibular size was identified between the pre-agricultural population and the farmers. Most regions of the mandible underwent shape changes. In conclusion, substantial changes in mandibular shape occurred throughout the Holocene Levant, especially following the agricultural revolution. These changes can be explained by the “masticatory-functional hypothesis”.
Highlights
The impact of dietary changes on mandibular morphology (e.g.1–4) and their implications in common oral disorders[1,5,6] have been discussed in many studies
The first two components of the Principal Component Analysis (PCA) of the form of the hemimandibles included in the study explain 62.5% of the variance based on the nine-landmark set (Fig. 1)
Since no significant differences in form were found between the post-Natufian populations, we combined them for the linear discriminant analysis (LDA)
Summary
The impact of dietary changes on mandibular morphology (e.g.1–4) and their implications in common oral disorders[1,5,6] have been discussed in many studies. Further changes were soon to follow with the introduction of cookware in the Pottery Neolithic period (8,400–6,500 cal BP); food preparation moved into a new phase, enabling lengthy cooking in pots (e.g.9,10,18–20) This advancement enlarged the variety of edible vegetables and elevated the amount of nutrients and energy that could be obtained from them, it reduced demands from the masticatory system (in force and time)[21]. Using Geometric morphometric methods may be a better way to examine the association between changes in dietary habits through time and changes in mandibular shape This approach has already been proven effective in identifying mandibular shape differences between populations that varied in subsistence strategy[1,2,3,33,44], and in determining the association between mandibular shape and muscle force[45,46] or biting performance[33]. The second, the post-industrial population (the modern population) will manifest different mandibular characteristics compared with the historic and prehistoric populations; and the third, the differences in form and shape will increase over time
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