Three-dimensional tooth surface texture analysis on stall-fed and wild boars (Sus scrofa)

Categorizing the archaeological remains of Sus scrofa as domesticated “pigs” or wild “boars” is often difficult because of their morphological and genetic similarities. For this purpose, we tested whether feeding ecological change of S. scrofa that accompanied their domestication can be detected based on the three-dimensional texture created on the tooth enamel surface by mastication. We scanned the lower tooth surface of one wild and one stall-fed populations of modern S. s. leucomystax and one wild population of S. s. riukiuanus by using a confocal laser microscope. The average body weight of S. s. leucomystax is twice as heavier as that of S. s. riukiuanus. The textures were quantified using the industrial “roughness” standard, ISO 25178, to prevent inter-observer errors and to distinguish small differences that were difficult to detect by two dimensional image observation. The values of parameters related to height and volume were significantly larger in the stall-fed population. Twenty parameters differed significantly between the stall-fed and wild population of S. s. leucomystax, which indicated that the feeding ecological difference affected the ISO parameters of the two boar populations. Six parameters also differed between the wild populations of S. s. leucomystax and S. s. riukiuanus. Surprisingly, no parameter differed between the populations of stall-fed S. s. leucomystax and wild S. s. riukiuanus. Consumption of hard nuts and/or agricultural fruits and crops by the wild population of S. s. riukiuanus may have produced a tooth surface texture similar to that of the stall-fed population of S. s. leucomystax. Further analysis of S. s. riukiuanus with a known diet is necessary to conclude whether ISO parameters reflect the dietary transition accompanying the domestication of Sus (e.g., wild, semi-domestic, and domestic). Until then, caution is needed in discriminating domesticated populations from wild populations that mainly feed on hard objects.