Incongruity between affinity patterns based on mandibular and lower dental dimensions following the transition to agriculture in the Near East, Anatolia and Europe

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.

Fig 1. Nine mandibular dimensions recorded following Bräuer (1988).

1. Ramus height (in projection). 2. Ramus breadth. 3. Maximum mandibular length (in projection). 4. Gonial breadth. 5. Bicondylar breadth. 6. Anterior height. 7. Anterior thickness. 8. Corpus height at M1/M2. 9. Corpus thickness at M1/M2.

Fig 2. Plot of the first two principal co-ordinates (explaining 62.6 and 16.9% of variation, respectively) based on mandibular form (raw data).

Fig 3. Plot of the first two principal co-ordinates (explaining 46.7 and 23.7% of variation, respectively) based on raw mesiodistal and buccolingual dental dimensions.

Fig 4. Composite of box plots for six of the mandibular shape variables among the four pre-defined subsistence and chronological groups.

In each case the pairwise dot table shows which groups were significantly different according to the posthoc results of the MANOVA (Table 3).