Abstract
While it has been suggested that malocclusion is linked with urbanisation, it remains unclear as to whether its high prevalence began 8,000 years earlier concomitant with the transition to agriculture. Here we investigate the extent to which patterns of affinity (i.e., among-population distances), based on mandibular form and dental dimensions, respectively, match across Epipalaeolithic, Mesolithic, and Neolithic samples from the Near East/Anatolia and Europe. Analyses were conducted using morphological distance matrices reflecting dental and mandibular form for the same 292 individuals across 21 archaeological populations. Thereafter, statistical analyses were undertaken on four sample aggregates defined on the basis of their subsistence strategy, geography, and chronology to test for potential differences in dental and mandibular form across and within groups. Results show a clear separation based on mandibular morphology between European hunter-gatherers, European farmers, and Near Eastern transitional farmers and semi-sedentary hunter-gatherers. In contrast, the dental dimensions show no such pattern and no clear association between the position of samples and their temporal or geographic attributes. Although later farming groups have, on average, smaller teeth and mandibles, shape analyses show that the mandibles of farmers are not simply size-reduced versions of earlier hunter-gatherer mandibles. Instead, it appears that mandibular form underwent a complex series of shape changes commensurate with the transition to agriculture that are not reflected in affinity patterns based on dental dimensions. In the case of hunter-gatherers there is a correlation between inter-individual mandibular and dental distances, suggesting an equilibrium between these two closely associated morphological units. However, in the case of semi-sedentary hunter-gatherers and farming groups, no such correlation was found, suggesting that the incongruity between dental and mandibular form began with the shift towards sedentism and agricultural subsistence practices in the core region of the Near East and Anatolia.
Highlights
Malocclusion is a condition caused by dental crowding and malposed teeth, that is very common among modern-day world populations, with an average prevalence of 20% [1]
The plot of the first two principal coordinates for mandibular form indicates a separation based on mandibular morphology between all hunter-gatherers and European agriculturalists (Fig. 2)
The results of the ANOVA carried out on mandibular size was significant (p < 0.001) with post-hoc analyses showing that the two hunter-gatherer groups and the transitional farmers all had significantly larger mandibles than the farmers, there was no significant differences among the three pre- or transitional farming groups (Table 2)
Summary
Malocclusion is a condition caused by dental crowding and malposed teeth, that is very common among modern-day world populations, with an average prevalence of 20% [1]. The condition has been described as the “malady of civilization” [5] and it has been hypothesized that the high prevalence of malocclusion and some of its related conditions (dental crowding, dental rotation) are associated with urbanization and, in some cases, industrialization [6,7]. The main factor believed to underlie this increase in the prevalence of malocclusion is an overall reduction in chewing stress, especially during mandibular and craniofacial growth, resulting in an incongruity between the size of the dental arcade and the jaw [6]. The etiological basis of this incongruity is the capacity of the (osseous) jaw tissue to react during ontogeny to changes in functional demands (phenotypic plasticity) while dental tissue does not remodel in response to biomechanical stress [8]
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