Proteomic identification of adhesive on a bone sculpture-inlaid wooden artifact from the Xiaohe Cemetery, Xinjiang, China

With the emergence and progress of composite tools in the Middle Stone Age, the adhesive became one of the most widely used materials by early human societies. However, the precise composition identification of adhesive in archaeological remains is a real analytical challenge, because the adhesive mainly consists of organic materials that are susceptible to decay during burial process. Of particular interest is to know which animal/plant species were being exploited for glue manufacturing other than for food. The arid climate of the Xiaohe Cemetery, located in Taklamakan Desert, northwestern China, provides favorable conditions for the preservation of organic residues. A bone sculpture-inlaid wooden artifact was collected from the Xiaohe Cemetery, with some semi-transparent yellowish adhesive exposed due to the detachment of an inlaid bone sculpture. In this paper, micro samples of the adhesive were scraped for FTIR (Fourier Transform Infrared Spectroscopy, primary examination) and subsequent proteomic analysis to determine the proteinous component(s) and precise origin(s). The identified tryptic peptides match most closely to known bovine collagen markers, suggesting that this adhesive was an animal glue made from cattle. These results reveal the diverse utilizations of cattle in the Xiaohe Cemetery, which provided not only meat, milk, hides, sinews and dung, but also leftover parts for manufacturing adhesive. This is the earliest evidence of adhesive identified in China up to our knowledge, which sheds light on adhesive development around 3500 years ago.