Ancient DNA reveals a family ossuary and long-distance migration on the Pacific coast before the Inca Empire

Abstract

This paper tracks long-distance migration on the Pacific coast that began no later than the thirteenth century AD. Genome-wide data for 21 sampled individuals from the lower and middle Chincha Valley of southern Peru show shared ancestry with groups 700 km to the north. A large-scale polity known as the Chincha Kingdom controlled the Chincha Valley from the thirteenth century until the fifteenth century, when it fell to the Inca Empire. The earliest migrants have unadmixed ancestry, whereas in subsequent generations, intermarriage resulted in admixtures from neighboring coastal areas. Relatives buried together in a family ossuary practiced consanguineous endogamy. We build a generation-scale Bayesian model informed by an aDNA-based family tree and individual calibration curves for estimated proportions of marine diet, addressing long-standing difficulties with temporal precision on the Pacific coast due to the marine reservoir effect and uncertainty inherent in estimating marine consumption based on d15N. These data demonstrate population continuity from the thirteenth to fifteenth centuries, coinciding with persistent traditions of cranial modification and postmortem red pigment application. We reveal close-knit and far-reaching coastal interaction networks that shaped the sociopolitical landscape encountered by Inca emissaries before they integrated these communities into their empire.