Saving Bones: a direct comparison of FTIR-ATR, whole bone percent nitrogen, and NIR

89th Annual Meeting of the American-Association-of-Physical-Anthropologists (AAPA), Los Angeles, CA, APR 15-18, 2020; International audience; Well-preserved collagen, an organic component of bone, can reveal much about the human past. While archaeological collagen can help illuminate the history of past populations, diagenetic processes can result in rapid and sometimes inconspicuous collagen degradation. As a result, recent sites may have poor preservation, while ancient sites may have some specimens that are surprisingly well-preserved. Consequently, there has been considerable interest in potential methods to prescreen bone for collagen content. Here we compare the efܪcacy of FTIR-ATR, whole bone percent nitrogen (%N), and NIR to select well-preserved samples from collections of unprocessed bone. FTIR utilizes the presence of Amide I (1651 cm-1) and Amide II (1553 cm-1) peaks and the Amide I/Phosphate peak-to-peak ratio to identify well-preserved specimen. A threshold of 0.76 %N suggests a sample preserves a sufܪcient amount of collagen. NIR uses chemometric models, built using PCA and PLSR of from specimens of known collagen yield, to characterize well-preserved specimens. Here, we compare FTIR-ATR and NIR spectra taken on samples from the Judean Desert, Israel, and the northern Saqqara region of Egypt. We then compare %N to NIR spectra from specimens from Zafarraya, a Neanderthal cave site in Spain. The results show agreement between FTIR-ATR and NIR, but among the Zafarraya collection, NIR correctly characterizes collagen content in 78.6% of samples compared to only 72.0% for %N. Near-infrared light proves to be advantageous because it penetrates deeply and can predict the collagen yield of unprocessed bone in a timely, cost-efficient, and non-destructive manner.