Long-distance migration along Peru’s Pacific coast began at least 800 years ago, centuries before the rise of the Inca Empire and much earlier than previously thought, a new international study reveals.

By analysing ancient DNA (aDNA) alongside archaeological and historical data, the study provides some of the strongest evidence to date of population movement along the Pacific coast prior to Inca rule (AD 1400 to 1532), demonstrating that pre-Inca coastal communities were far more mobile and connected at local and interregional scales than historically believed.

Published in Nature Communications, it suggests people travelled more than 700 kilometres from Peru’s north coast to the Chincha Valley in the south. Here, they settled and intermarried with neighbouring populations, while maintaining distinctive cultural traditions – such as cranial modification and painting the dead with red pigment – for generations. The study also identified a single grave containing relatives who engaged in endogamy, or close-kin procreation.

“Migration and kinship have long been part of the human story and the development of powerful societies,” said co-lead author Dr Jacob Bongers, digital archaeologist and member of the Vere Gordon Childe Centre at the University of Sydney, and Visiting Research Fellow at the Australian Museum Research Institute.

“What’s most interesting about this research is that it shows the close-knit and far-reaching social networks of pre-Inca coastal communities, as well as how people maintained cultural traditions of marking group identities for centuries, even as they intermarried with distinct groups,” he said.

Tracing ancient movement through aDNA

The research team analysed aDNA samples of 21 individuals recovered from burial sites in the Chincha Valley to reconstruct family relationships and explore genetic diversity over time.

“The genome-wide data and radiocarbon dates suggest migrants arrived in the Chincha Valley by at least the thirteenth century AD, well before Inca expansion,” Dr Bongers said. “Their ancestry traced back to the Peruvian north coast, more than 700 kilometres away, and the aDNA of these early migrants revealed no evidence of mixing with local populations.”

Genetic evidence revealed mixed ancestry between people from the north, central and south coasts over subsequent generations. “This likely means that, after northerners migrated to Chincha, they intermarried with groups from neighbouring coastal areas, a practice that continued during the Spanish Colonial Period (AD 1532-1825),” Dr Bongers said.