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Nomadic ecology shaped the highland geography of Asia’s Silk Roads

Nature volume 543, pages 193198 (09 March 2017) | Download Citation


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.

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Funding for research at the SAIE laboratory was provided by Washington University in St. Louis (M.D.F.). C. Copp and M. Webb provided assistance with modelling and coding in the SAIE laboratory and GIS laboratory of Washington University in St. Louis. C. Chady assisted in copy editing. An early version of the pastoralist participation model was presented at the Advanced Seminar ‘New Geospatial Approaches in Anthropology’ at the School for Advanced Research, March 6–10, 2016. P. Daly, R. Pinhasi, G. Larson and D. Meltzer provided commentary on drafts of this article.

Author information


  1. SAIE Laboratory, Department of Anthropology, Washington University in St. Louis, 1 Brookings Drive, CB 1114, St. Louis, Missouri 63130, USA

    • Michael D. Frachetti
    •  & C. Evan Smith
  2. University Libraries, Washington University in St. Louis, 1 Brookings Drive, CB 1061, St. Louis, Missouri 63130, USA

    • Cynthia M. Traub
  3. Institute of Archaeology, University College London, 31–34 Gordon Square, London WC1H 0PY, UK

    • Tim Williams


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M.D.F. conceptualized the study, designed, and executed the spatial model, and wrote the manuscript with editing and approval from C.E.S., T.W. and C.M.T. C.E.S. carried out spatial modelling and script coding in ArcGIS and Python. C.M.T. carried out statistical modelling and analysis of the results. T.W. provided the Silk Road site database and contributed to analysis and interpretation of the results. M.D.F. carried out spatial and statistical analysis and interpretation of the results with contributions and input from C.E.S., C.M.T. and T.W.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Michael D. Frachetti.

Reviewer Information Nature thanks D. Rogers and the other anonymous reviewer(s) for their contribution to the peer review of this work.

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    Supplementary Information

    This file contains the Supplementary Discussion, Supplementary References, Supplementary Table 1, a link to the executable ArcPython script to run the PastPart model in ArcGIS and the statistical report providing comprehensive data and illustration of the range of statistical analysis carried out for this study.

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