Para-masticatory wear facets and their functional significance in hunter–gatherer maxillary molars

The mastication of tough and hard foods combined with the extensive use of teeth as tools, have been considered possible antemortem causes in determining enamel microfractures of the tooth crown. This phenomenon, known as dental chipping, has been found in different fossil hominins and in several pre-historic and historic human populations who adopted different subsistence strategies. However, little is understood of the mechanism, function and the formation of dental chipping.     

An investigation of the frequency of squatting facets in Later Stone Age foragers from South Africa

Distinctive morphological changes attributed to a habitual squatting posture were observed on the distal femur, distal tibia and on the talar neck of Later Stone Age (LSA) foragers. The frequency of squatting in LSA foragers (n = 56) was determined by the presence of anatomical features of joint hyperflexion. Three South African comparative skeletal groups from different time periods were also analysed: skeletal remains of early farming populations (n = 17), 18th century ‘Free Blacks’ and/or slaves from Cobern Street, Cape Town (n = 21), and a modern cadaver sample (n = 29). The results show that 28 out of 56 LSA foragers (50%) were habitual squatters; 13 out of 17 farmers (76.5%) and one of 21 individuals from the Cobern Street collection (4.8%) demonstrated squatting facets. No anatomical squatters were found in the modern cadaver sample. There was no significant sex difference between squatters and non‐squatters. Hence at least half of the LSA foragers and farmers were habitual squatters, according to the signs of joint hyperflexion. Squatting is a comfortable position for those used to it because the body weight is supported with minimal muscular activity. Two probable reasons are suggested for the difference in postures adopted by the different groups: (1) availability or lack of availability of furniture and (2) cultural and individual differences in resting posture. Copyright © 2005 John Wiley & Sons, Ltd.     

Grain‐scale permeabilities of faceted polycrystalline aggregates

Porous synthetic quartzites and amphibolites, each with faceted pore walls, were synthesized and evaluated to examine the permeability of pore networks similar to those of the lower crust and mantle. Quartzite with a fluid in equilibrium with an Mg–clinopyroxene contained connected networks of pores with a dihedral angle of 30° bounded by walls that were 10–50% faceted. The relationship of their permeability (k) to porosity (φ) is approximated by the previously determined relationship for relatively nonfaceted synthetic quartzite Amphibolite with an HF fluid contained fluorotremolite and a connected network of pores bounded by walls exhibiting 78–90% faceting. These materials showed much lower k for a given φ, with an apparent permeability threshold at φ_c = 0.04. A curve fit to these data yields The results suggest that moderate faceting has little effect on the transmission of fluids through rocks, but extensive faceting significantly alters permeability. This difference is most likely produced through isolation of the fluid to the grain corners at low φ with extensive faceting. Rocks with pores that tend toward faceting may impede the flow of fluids and melt.