Chemical profiling of ancient hearths reveals recurrent salmon use in Ice Age Beringia

Current approaches to reconstruct subsistence and dietary trends inancient hunter-gatherer societies include stable isotope analyses,but these have focused on human remains, cooking pottery, andfood residues, which are relatively rare in the archaeological record.In contrast, short-term hearths are more ubiquitous worldwide, andthese features can provide valuable evidence for ancient subsistencepractices, particularly when faunal remains are not preserved. Totest the suitability of hearths for this purpose, we conducted mul-tiple chemical analyses: stable carbon and nitrogen isotope analysesof total organic matter (expressed asδ13Candδ15N values) andcompound-specific carbon isotope analyses of individual fatty acids(δ13C16:0andδ13C18:0) from 17 well-preserved hearths present inthree occupations dating between∼13,200–11,500 calibrated yearsB.P. at the Upward Sun River (USR) site in central Alaska. We com-binedδ15Nandδ13CFAdata in a Bayesian mixing model (stable iso-tope analysis in R) with concentration dependency to each hearth.Our model values were tested against faunal indices, indicating astrong positive relationship between marine proportional contribu-tions to each hearth and salmon abundance. Results of the modelsshow substantial anadromous salmon use in multiple USR compo-nents, indicating recurrent use of the site for salmon processingduring the terminal Pleistocene. Our results demonstrate that sal-monid and freshwater resources were more important for late Pleis-tocene hunter-gatherers than previously thought and highlight thepotential of chemical profiling of hearth organic residues for pro-viding greater geographic and temporal insights into resource useby prepottery societies.We thank T. Howe and N. Haubenstock for instrumental assistance with GC-C-IRMS analysis; S. Billings for assistance with GC-MS; A. Schimmelman for providing fatty acid isotope standards; T. Howe and S. Billings for providing hunted modern animal samples in Interior Alaska; and Caitlin Holloway for providing laboratory assistance. This project was funded in part by National Science Foundation Grants OPP-0732846, OPP-1137078, OPP-1138811, and OPP-1223119