Incongruity between Affinity Patterns Based on Mandibular and Lower Dental Dimensions following the Transition to Agriculture in the Near East, Anatolia and Europe

The title of this paper is written in “academese” so it is somewhat confusing. The research is about teeth crowding in the lower jaw among pioneering farmers in the Near East versus healthy teeth among hunter gatherers. Here is the 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.

What is odd about this paper is that the researchers’ conclusion is incorrect. They write:

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].

Jaw narrowing, as well as a host of other maladies, is due to malnutrition that is associated with high carbohydrate/low meat protein and fat diets. Mike Eades wrote a good article about this: “Nutrition and health in agriculturalists and hunter-gatherers“. He quotes the conclusion of a paper that compared the health of hunter gatherers to that of farmers.

Here is the summary of the findings of this analysis of skeletal data as tabulated by the author:

1.    Life expectancies for both sexes at all ages were lower at Hardin Village than at Indian Knoll.
2.    Infant mortality was higher at Hardin Village.
3.    Iron-deficiency anemia of sufficient duration to cause bone changes was absent at Indian Knoll, but present at Hardin Village, where 50 percent of cases occurred in children under age five.
4.    Growth arrest episodes at Indian Knoll were periodic and more often of short duration and were possibly due to food shortage in late winter; those at Hardin Village occurred randomly and were more often of long duration, probably indicative of disease as a causative agent.
5.    More children suffered infections at Hardin Village than at Indian Knoll.
6.    The syndrome of periosteal inflammation was more common at Hardin Village than at Indian Knoll.
7.    Tooth decay was rampant at Hardin Village and led to early abscessing and tooth loss; decay was unusual at Indian Knoll and abscessing occurred later in life because of severe wear to the teeth.  The differences in tooth wear and caries rate are very likely attributable to dietary differences between the two groups.

Her analysis based on this data:

Overall, the agricultural Hardin Villagers were clearly less healthy than the Indian Knollers, who lived by hunting and gathering.

H/T Past Horizons.

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