Masticatory function and post‐pleistocene evolution in Nubia

Abstract

The present research focuses on craniofacial variation in Nubia over approximately 10,000 years. Samples were grouped according to their temporal location and subsistence pattern, and represent a transition from a hunting-gathering adaptation (Mesolithic) to a transitional hunting-gathering-agricultural adaptation (A-C Group) and finally to a fully agricultural adaptation (Meroitic/X-Group/Christian). The purposes were: (1) to compare the Mesolithic sample with the later Nubian populations; and (2) to evaluate further the hypothesis that change in Nubian craniofacial morphology was due to changing functional demands associated with the progressive change in subsistence adaptation and associated behavior. The results tend to support recent views that the Nubian Mesolithic population is probably ancestral to later Nubian groups, and that the masticatory-functional hypothesis can best account for craniofacial change among the Nubians since 12,000 B.P. According to this hypothesis systematic reduction in functional demand placed on the masticatory complex from the Mesolithic led, secondarily, to an alteration of the growth of the maxillomandibular complex such that the face became progressively less robust and more inferoposteriorly located relative to the cranial vault. Both the increase in the height of the vault relative to its length, producing a more "globular" appearance, and the reduction in dental size were tertiary, compensatory responses to altered facial size and position.

Diffusion, Biological Determinism, and Biocultural Adaptation in the Nubian Corridor

“…Through time, the vault became more rounded and anteriorly placed, the face more inferiorly placed, and the skull relatively shorter, with more posteriorly located masseter and temporalis muscles. In agreement with Greene's earlier analysis of the dental evidence, Carlson (1976a, b) and Carlson and Van Gerven (1977) concluded that the total pattern of dental reduction and reorientation of face and vault was the result of a reduction in masticatory stress associated with the transition from Mesolithic to Neolithic subsistence patterns. Although the mechanisms by which that morphological trend came about cannot be determined precisely, the most reasonable explanation emphsizes progressive alterations in maxillomandibular growth in response to developmental variation in the size and position of the muscles of mastication, i.e., the masticato7y-functional hypothesis (see Figure 2) (Carlson 1976b;Carlson and Van Gerven 1977).…”

“…In agreement with Greene's earlier analysis of the dental evidence, Carlson (1976a, b) and Carlson and Van Gerven (1977) concluded that the total pattern of dental reduction and reorientation of face and vault was the result of a reduction in masticatory stress associated with the transition from Mesolithic to Neolithic subsistence patterns. Although the mechanisms by which that morphological trend came about cannot be determined precisely, the most reasonable explanation emphsizes progressive alterations in maxillomandibular growth in response to developmental variation in the size and position of the muscles of mastication, i.e., the masticato7y-functional hypothesis (see Figure 2) (Carlson 1976b;Carlson and Van Gerven 1977). More specifically, according to that hypothesis, the change in diet associated with the transition from the Mesolithic through the Christian periods in Nubia brought about a reduction in required neuromuscular activity for the muscles of mastication and thus a decrease in the stress placed on the teeth and jaws.…”

“…Those features in the Nubian population from Mesolithic times are similar to features found over a wide geographic area in earlier Paleolithic material, as well as in contemporary aboriginal Australian populations (Greene and Armelagos 1972). Such a broad geographic and temporal distribution suggests similar adaptation rather than common racial origin and migration (Carlson and Armelagos 1971;Carlson and Van Gerven 1977).…”

“…Recent multivariate analyses were undertaken by Carlson (1976a, b) and Carlson and Van Gerven (1977) in order to account for craniofacial variation in the populations of Lower Nubia over a 10,000-year period (Mesolithic through Christian). That research revealed one principal diachronic pattern of change.…”

Technical Note: The Definition of New Dental Morphological Variants Related to Malocclusion

“…Dental crowding and malocclusion are often discussed in relation to the adoption of agriculture and the introduction of soft foods as part of the masticatory-functional hypothesis (Carlson and Van Gerven, 1977;Corruccini, 1984;Corruccini et al, 1983;Larsen, 2015). In this discussion, malocclusion encompasses two distinct features: malalignment of the teeth (i.e., crowding) and malalignment of the jaws (i.e., overbite and underbite).…”