Doctoral Dissertation Improvement: The Effects of Food Processing on Mechanical Properties and Masticatory (Chewing) Performance

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Processing food is a universal human behavior. The effects of food modification on hominin biology are poorly understood, however, and most research focuses on thermal processing (cooking), leaving non-thermal, mechanical processing methods largely unstudied. To address these gaps in understanding, this research tests the effects of simple mechanical processing (pounding and slicing) and cooking (roasting) on masticatory (chewing) performance. The general hypothesis tested is that the effects of mechanical processing on food material properties may help account for dental size reductions within the genus Homo prior to the adoption of cooking. To test this hypothesis, 14 subjects will chew size-standardized samples of raw or processed food. EMG (electromyographic) recordings of muscle activity and correlated bite-force data will be collected from masticatory muscles and a predictive model used to determine whether mechanical processing can account for tooth size decreases prior to the Middle Paleolithic, when archeological evidence for cooking first becomes abundant. The efficiency of food breakdown in the mouth (rate of food fragmentation per chew) and data on the foods' mechanical properties will also be collected. Intellectual merits- This study is among the first to assess how cooking and mechanical processing of representative foods affect key biomechanical properties of mastication such as chew number, force production and food fragmentation efficiency. There has been much debate concerning cooking in human evolution, but while this study experimentally tests the masticatory performance effects on roasted foods, it also tests other potentially important forms of food processing that probably predate cooking, notably mechanical tenderization and slicing. Broader Impacts- This research promotes graduate education and will result in a Ph.D. for a female graduate student. Additionally, the data generated will increase knowledge on hominin diets, food mechanical properties, processing effects and chewing performance. Given interest in cooking and other food processing techniques, the results are relevant to a wide variety of fields including anthropology, food science, evolutionary biology and anatomy.