Dental microwear analysis is a tried-and-true method of reconstructing the diets of living and extinct animals – including early hominins and Homo sapiens – from prehistory to the present day. Microwear can be thought of as the microscopic “pits” and “scratches” that form on the tooth surfaces as food is chewed. The foods we consume, the ways foods are processed and prepared, and the particles that are ingested with food (e.g., dust and grit from the environment, particles worn off grindstones or milling devices, etc.) all influence the microscopic wear patterns on tooth surfaces. Microwear ”texture” is a way of quantifying wear in three-dimensions using standardized variables that reflect the directionality, size, depth, and other characteristics of enamel microwear (see the example below). Thus, microwear variation by group or individual can reveal a great deal of information concerning diet and past human lifeways. Photosimulations (left) and 3D representations of microwear textures. wear. The top two are from a Natufian forager, the middle two are from a Roman-era farmer from Herculaneum, and the bottom two are from a Mongolian pastoralist. The dark colors are low points and the hot (white/red) are higher points. Contemporary culinary traditions are vast, but prehistoric and historic diets also varied incredibly. In a pre-globalized world, eating local and less mechanically processed foods would have been the norm, local environmental conditions would have had an extensive influence on the types of foods available, and cultural practices would dictate how those foods were prepared. So, the grains, fruits, vegetables, tubers, meat and anything else you can think of stuffing down your gullet are only part of what influences microwear signatures on teeth. Other aspects to consider are whether these foods are wild or domestic, raw or cooked, grilled or boiled, salted or fermented, and so on and so on... One way of teasing out these influences on microwear signatures in archaeological contexts is through the creation of large comparative databases that include human groups with extensive spatial, temporal, environmental, and cultural variation – variation that would, in turn, also influence dietary variability. This is exactly what Christopher Schmidt (University of Indianapolis) and a team of 24 researchers set out to do using a global sample of 719 individuals from 51 archaeological sites (see map below). Locations of groups sampled in the study. Details of chronology, archaeology, subsistence, and more can be found in the original article. Schmidt and colleagues tested three main hypotheses to better understand the utility of microwear texture analysis for paleodietary reconstruction. We (yep, I was a co-author in the study), lumped the individuals studied into 3 general subsistence categories: 450 farmers, 192 foragers, and 77 pastoralists. Foragers gather, hunt, and/or fish for their sustenance; primarily consume non-domesticated foods; and generally process foods to a lesser degree than farming and pastoralist groups. Farmers tend to consume a diet dominated by domesticated plants, most frequently grains; and frequently use more intensive food processing (milling, grinding, boiling, etc.) than foragers which contributes to softer diets. Pastoralists are typically very mobile people relying on animal husbandry. Dietary staples such as cheese, meat, and yogurt are consumed but frequently supplemented with grains. Thus, pastoralists diets are generally soft with some abrasive content. However, these categories are NOT hard-and-fast distinctions. Instead, subsistence variation within these categories is HIGHLY variable, but broad categories allowed us to test for broad differences between groups. We found that important differences are found between the “big three” subsistence categories (see figure below). However, there were also interesting differences between foragers and farmers in the New World and Old World as well as interesting differences through time in the Old World farmers. Scatter Plot with the mean (central point) and standard deviations (lines) of the two microwear variables analyzed in the study. Some broad differences can be seen but the substantial overlap in subsistence groups can also be seen. Without getting into too much detail about the finer differences acknowledged in the study, I’d rather come back to the initial point I made about variability within the macro-categories we are using. Keep in mind that each comparative sample is unique because of the circumstances in which those people lived – e.g., local climate, environments, food availability, and the culinary traditions they practiced among other factors. However, each group also has its own internal variability related to things like age, sex, social status, etc. All of this variation is bound to make for extremely interesting case studies as the human groups in this study are are re-analyzed and published as individual case studies. Aside from being very happy to participate in this study, I am really looking forward to the individual papers that my co-authors will be preparing on the samples they contributed here.
Full Article: Schmidt CW, Remy A, Van Sessen R, Willman J, Krueger K, Scott R, Mahoney P, Beach J, McKinley J, d’Anastasio R, Chiu LW, Buzon M, De Gregory R, Sheridan SG, Eng J, Watson J, Klaus H, Da-Gloria P, Wilson J, Stone A, Sereno P, Droke J, Perash R, Stojanowski C. Herrmann, N. Dental microwear texture analysis of Homo sapiens sapiens: Foragers, farmers, and pastoralists. American Journal of Physical Anthropology, 169(2), 207-226, https://doi.org/10.1002/ajpa.23815. If you’re interested in other research on prehistoric diets, I strongly urge you to get a hold of one of these popular accounts by Peter S. Ungar: The Real Paleo Diet. Scientific American, 319(1), 42-49. Evolution's Bite A Story of Teeth, Diet, and Human Origins https://press.princeton.edu/titles/10943.html
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John C. Willman
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