Evidence of silk found in Bronze Age sacrificial pits

China National Silk Museum and the Sichuan Research Institute of Cultural Relics and Archaeology have confirmed the use of silk in sacrificial rituals by a Bronze Age civilization in the Yangtze River Basin. The findings provide direct archaeological evidence that silk was used as a material during rituals at the Sanxingdui site in Sichuan, China.

Silk was a pivotal material in the development of global trade along the Silk Road, which derives its name from the extensive trade of silk along its routes. The origins of silk use have been difficult to trace due to its organic composition and susceptibility to degradation, leaving little direct evidence in archaeological records, though implements related to silk manufacturing can be found during the Neolithic period.

At the Sanxingdui site, layers of ash and burned artifacts, including bronze and jade, have been uncovered in eight sacrificial pits dating to the late Shang Dynasty (1600–1100 BCE). Among these, a unique bronze “grid-like ware” with embedded jade was discovered with traces of fabric, prompting researchers to investigate whether silk was among the remnants.

In the study, “Evidence of the use of silk by Bronze Age civilization for sacrificial purposes in the Yangtze River basin of China,” published in Scientific Reports, researchers utilized advanced analytical methods to identify silk residues.

Techniques included immunoaffinity column (IAC) enrichment combined with enzyme-linked immunosorbent assay (ELISA), scanning electron microscopy (SEM), and proteomics. These methods enabled the detection of mineralized silk residues in severely degraded samples.

Samples were extracted from mineralized fabric traces found on bronze and jade artifacts and from within the ash layers of a sacrificial pit. Silk fibroin, the protein at the core of silk’s structure, was analyzed using IAC-enriched samples. ELISA testing confirmed silk fibroin’s presence in mineralized fabric remnants and ash layers. Morphological observation via SEM revealed that the fibers exhibited a smooth, triangular cross-section characteristic of silk.

Proteomic analysis identified fibroin’s heavy chain (P05790 protein) in both archaeological and simulated soil samples, confirming the material’s identity as silk. It was further able to identify mulberry silk (Bombyx mori) as the material used, demonstrating that sericulture (silk farming) involved the cultivation of mulberry trees to feed silkworms, corroborating historical accounts.

The complete analysis revealed that fabrics found in the Sanxingdui pits included silk and that silk residues were partially preserved due to mineralization processes facilitated by copper ions released from bronze artifacts.

Silk traces were found wrapped around jade artifacts and covering the bronze grid-like ware, suggesting their use in ritual contexts. The uneven mineralization of the fibers and the presence of ash-layer silk residues indicated that not all silk was fully incinerated during these rituals.

The researchers suggest that silk was used as a “material carrier” in religious ceremonies to communicate between Heaven and Earth, aligning with historical records of silk being used for sacrificial temple clothing and rituals in ancient China. The Sanxingdui discoveries also provide insight into early silk farming practices in the region.

Previous radiocarbon dating of the site provides a range of approximately 3,148–2,966 years before the present, placing it among the oldest examples of silk fibers ever found and at a location still known for its production today. The historical accounts about silk farming in ancient China are mostly related to the land of the Shu State. Silk farming in the broader Yangtze River region, including areas near Sanxingdui, began over 5,000 years ago during the Neolithic period.

The findings confirm the cultural significance of silk in the early Bronze Age and the technological innovations of the ancient Shu civilization in a region still known for mulberry tree-fed silk farming and as the world’s biggest producer and exporter of silk.

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