Birch bark tar ornaments: identification of 2000-year-old beads and bracelets in southwest China

Birch bark tar is one of the oldest man-made organic materials, which was most commonly served as adhesives in ancient Eurasia, but little is known about its usage in personal ornaments. In this study, we present the earliest direct evidence for the specific use of birch bark tar in the production of ornaments through chemical investigation (including FTIR, GC/MS, and Py-GC/MS) and imaging examination (including SEM and micro-CT). The chemical and microscopic analyses indicate that some beads and bracelets unearthed from a public cemetery (the Dayuanzi site) of an ancient state or tribe (Xinan Yi) on the eastern Yunnan plateau in southwest China dated to approximately 475 BCE-8 CE were exclusively made with birch bark tar. These ornaments represent a unique cultural phenomenon among ethnic groups in this region, which may contribute to a better understanding of plant exploitation and the related birch bark culture among different cultural groups and their interrelationships in the past.

Automated summary

This study provides the earliest direct evidence of the specific use of birch bark tar in the production of ornaments through chemical and microscopic analyses. These ornaments, found in a public cemetery in southwest China, represent a unique cultural phenomenon among different ethnic groups and contribute to a better understanding of plant exploitation and cultural interrelationships in the past.