Anthropology, University of Notre Dame
April 16, 2020 , Platinum Ballroom
The non-shivering thermogenic capacity of brown adipose tissue (BAT) indicates a possible evolutionary function in human cold adaptation. Previous studies demonstrated the significant metabolic activity of BAT in cold-adapted populations. However, no studies have looked at BAT activity in a tropical sample. Polynesian morphology defies traditional eco-geographical rules, which has spurred many evolutionary theories to explain this phenotype. Measuring BAT in a Polynesian sample will elucidate the range of BAT activity and address the cold-adapted Polynesian morphology paradox. In this study we assessed the metabolic activity of BAT in a temperate-climate sample in hopes of extrapolating the likely presence of and variation in BAT activity in a tropical population. In our study we inferred seasonal patterns of BAT activity by combining metabolic rate (MR) measurements and thermal imaging of the suprascapular region under room temperature (RT) and mild cold exposure (CE) in upstate New York (n=75, female n=46, ages: 18-63). Independent of the season, suprascapular skin temperature significantly decreased (p<0.001) and MR significantly increased (p<0.05) after cooling. Comparing winter and summer measurements, MR increases were not significant, while suprascapular skin temperatures were significantly higher in the winter (p<0.001). These results indicate seasonal patterns of BAT activity in a temperate-climate sample, even in summer. This suggests an increased likelihood of detecting BAT activity in a tropical sample, promoting the need to analyze BAT activity in a Polynesian sample. Such a study will determine BAT variation in warmer climates and infer the role of physiological adaptations in the peopling of Polynesia.