A Partial Prehistory of the Southwest Silk Road: Archaeometallurgical Networks along the Sub-Himalayan Corridor

Historical phenomena often have prehistoric precedents; with this paper we investigate the potential for archaeometallurgical analyses and networked data processing to elucidate the progenitors of the Southwest Silk Road in Mainland Southeast Asia and southern China. We present original microstructural, elemental and lead isotope data for 40 archaeological copper-base metal samples, mostly from the UNESCO-listed site of Halin, and lead isotope data for 24 geological copper-mineral samples, also from Myanmar. We combined these data with existing datasets (N = 98 total) and compared them to the 1000+ sample late prehistoric archaeometallurgical database available from Cambodia, Laos, Thailand, Vietnam and Yunnan. Lead isotope data, contextualized for alloy, find location and date, were interpreted manually for intra-site, inter-site and inter-regional consistency, which hint at significant multi-scalar connectivity from the late second millennium bc. To test this interpretation statistically, the archaeological lead isotope data were then processed using regionally adapted production-derived consistency parameters. Complex networks analysis using the Leiden community detection algorithm established groups of artefacts sharing lead isotopic consistency. Introducing the geographic component allowed for the identification of communities of sites with consistent assemblages. The four major communities were consistent with the manually interpreted exchange networks and suggest southern sections of the Southwest Silk Road were active in the late second millennium bc.