Factors affecting molar size in Sus scrofa

摘要

Teeth are thought to be less affected than post-cranial elements by factors such as age, region, sex, and post Pleistocene climate change, making changes in tooth size a better gage of domestication-induced morphological change in Sus scrofa. Rigorous empirical evaluation of this assumption, however, has been lacking. Here we examine the impact of multiple factors on molar size in an assemblage of modern wild boar from Southwest Asia, as well as a large assemblage of ancient S. scrofa from an archaeological site in southeastern Turkey dated to 11,600 cal. BP. We find that age related interstitial wear has a profound impact on molar lengths. Comparisons of length measurements of S. scrofa molars should only be made if one strictly controls for the state of wear, as well as the stage of crown development and eruption in third molars. Breadth measurements, on the other hand, are little affected by progressive wear and, as a result, are preferable to length measurements in the analysis of molar size in S. scrofa. We also evaluate the impact of logarithm size index (LSI) scaling on molar dimensions. Molar lengths are subject to a number of factors that distort meaningful patterning rendering LSI values of length dimensions of little utility in the evaluation of molar size in S. scrofa. With the exception of the upper first molar, LSI values of molar breadths appear to both capture and amplify patterns seen among unconverted measurements of individual teeth. Our evaluation also confirms the assumption that the size of post-cranial elements is more profoundly affected than molars by factors such as region and Post-Pleistocene climate change. While sexual dimorphism also has a greater impact on the size of post-crania than on molars, the degree of sexual dimorphism in molar breadths, as well as in M3 lengths, is still substantial and must be taken into account in any study of S. scrofa molar size. Before interpreting downward shifts in molar size as an indicator of domestic status, archaeozoologists need to first to consider the possible impact of differences in the proportions of males and females in archaeological assemblages. We conclude with a number of recommendations for new protocols for the analysis of S. scrofa dental metrics. We also offer observations about the impacts of factors like region, sex, and change over time on the size of the molars of this species that may open up new areas of research.