Nomadic ecology shaped the highland geography of Asia’s Silk Roads
Michael D. Frachetti1, C. Evan Smith1, Cynthia M. Traub2 & Tim Williams3
There are many unanswered questions about the evolution of the ancient ‘Silk Roads’ across Asia. This is especially the case in their mountainous stretches, where harsh terrain is seen as an impediment to travel. Considering the ecology and mobility of inner Asian mountain pastoralists, we use ‘flow accumulation’ modelling to calculate the annual routes of nomadic societies (from 750 m to 4,000 m elevation). Aggregating 500 iterations of the model reveals a high-resolution flow network that simulates how centuries of seasonal nomadic herding could shape discrete routes of connectivity across the mountains of Asia. We then compare the locations of known high-elevation Silk Road sites with the geography of these optimized herding flows, and find a significant correspondence in mountainous regions. Thus, we argue that highland Silk Road networks (from 750 m to 4,000 m) emerged slowly in relation to long-established mobility patterns of nomadic herders in the mountains of inner Asia.
The Silk Road refers to a network of ancient trade routes that have crossed central Asia since time immemorial. But how did it get started? Conventional models usually start by inferring the easiest paths between sites already known to be part of the network. This introduces a circular argument as it biases the results towards what is already known. Here Michael Frachetti and colleagues take a different approach to show that the network emerged from hundreds of years of interactions between pastoralists moving their livestock between higher and lower elevations in response to the seasons in this generally mountainous region. They suggest that the Silk Road network therefore materialized slowly from the long-established, local mobility patterns of nomadic herders. This finding may encourage archaeologists to seek more nuanced explanations for the evolution of ancient connectivity.