Genomic admixture tracks pulses of economic activity over 2,000 years in the Indian Ocean trading network

Nicolas Brucato,Pradiptajati Kusuma,François-Xavier Ricaut,Murray P Cox,Philippe Beaujard,Herawati Sudoyo

doi:10.1038/s41598-017-03204-y

Abstract

The Indian Ocean has long been a hub of interacting human populations. Following land- and sea-based routes, trade drove cultural contacts between far-distant ethnic groups in Asia, India, the Middle East and Africa, creating one of the world’s first proto-globalized environments. However, the extent to which population mixing was mediated by trade is poorly understood. Reconstructing admixture times from genomic data in 3,006 individuals from 187 regional populations reveals a close association between bouts of human migration and trade volumes during the last 2,000 years across the Indian Ocean trading system. Temporal oscillations in trading activity match phases of contraction and expansion in migration, with high water marks following the expansion of the Silk Roads in the 5th century AD, the rise of maritime routes in the 11th century and a drastic restructuring of the trade network following the arrival of Europeans in the 16th century. The economic fluxes of the Indian Ocean trade network therefore directly shaped exchanges of genes, in addition to goods and concepts.

Highlights

For more than 2,000 years, the Indian Ocean rim has been an area of intense interaction between African, Middle Eastern and Asian populations, driven by a strong tradition of wealthy maritime and land-based trading routes[1, 2]
Long corridors of genetic similarity can be seen along the coasts of East Africa, South Asia and the rim of the China Sea, and strong genetic barriers such as one observed between South Asia and East Africa (Supplementary Figure 1)
Consistent with the idea that trading activities stimulate biological contacts, both analyses indicate that migration is highly correlated with historical trading volumes[9] (r2 = 0.89, P = 0.00001; Fig. 1; Supplementary Tables 4, 5 and Supplementary Figure 7)

Summary

Introduction

For more than 2,000 years, the Indian Ocean rim has been an area of intense interaction between African, Middle Eastern and Asian populations, driven by a strong tradition of wealthy maritime and land-based trading routes[1, 2]. Genome-wide genetic variation in 3,006 individuals from 187 regional populations was used to build a picture of gene flow around the Indian Ocean rim over the past 2,000 years (Supplementary Table 1). The genetic landscape of the Indian Ocean rim today, as characterized by ADMIXTURE11 and EEMS12, is a structured space with distinct regional genetic ancestries allowing the fine-scale reconstruction of historical human migrations mediating gene flow (Supplementary Figures 1–6).

Results

Conclusion