Same, Same or Different? Applying Zn Isotope Analysis to Understand Subsistence Practices in Ancient Myanmar

Anna Willis1*, Baptiste Pradier2, Alex McCoy-West1, and T.O Pryce3

Thousands of years ago, the domestication of millet in the Yellow River region and rice in the Yangtze River region began transforming the subsistence economies of communities in the region. Evidence suggests rice farmers from southern China moved into mainland Southeast Asia, but little is known about the origins of agriculture in Myanmar. Recently, stable carbon isotope analysis has provided valuable insight into the subsistence practices there. With different photosynthetic pathways, rice (C₃) and millet (C₄) have distinct δ¹³C values. Our findings indicate that individuals in Myanmar consumed more C₄ plants than those in mainland Southeast Asia. These may reflect regional differences in cropping systems (millet vs. rice), animal feeding practices (foddered vs. grazed), or protein sources (plant vs. animal). Unable to determine this from the available data, we undertook zinc isotope analysis. As a powerful dietary tracer, δ⁶⁶Zn has been successfully used as an alternative to δ¹⁵N in samples where collagen is poorly preserved, providing information on the trophic levels of consumed dietary resources and the relative amount of animal and plant protein. We measured δ⁶⁶Zn in tooth enamel of individuals from two communities in ancient Myanmar, excavated by the Mission Archéologique Française au Myanmar (MAFM) between 2014 and 2020. We assessed variation in δ⁶⁶Zn and compared the findings to previously published isotope data (δ¹³C, δ¹⁸O, ⁸⁷Sr/⁸⁶Sr), measured in the same teeth. Situated within the local and wider regional context, these findings provide a deeper understanding of the subsistence economy in ancient Myanmar.