Europe is not enough

Almost all people of European descent can trace their paternal origins back to inhabitants of the Eurasian steppe. In recent years, it has become clear that these people, known as the Yamnaya, and their descendants travelled across the continent during the Neolithic replacing locals – particularly the men – as they went (see main story). Now we have discovered the Yamnaya also migrated east.

A study by David Reich at Harvard Medical School and his colleagues posted to the bioRxiv preprint server in 2018 gives us an idea of when and how this happened. Using DNA samples from the remains of hundreds of people who lived across south Asia between about 7000 and 3000 years ago, the team found evidence that Yamnaya-related DNA began appearing there between 4000 and 3000 years ago.

Those steppe pastoralists mingled with people who may have been related to the inhabitants of the famous Indus Valley Civilisation. In doing so, they formed an “Ancient North Indian” population, one of the two ancestral populations that define the ancestry of most people living in the Indian subcontinent today. What’s more, incomers from the steppe may have brought major cultural changes. Speaking at New Scientist Live in September, Reich pointed out that people in the Indian subcontinent today who carry the largest amounts of Ancient North Indian ancestry tend to speak similar languages to one another, and often (but not always) belong to upper castes.

As in Europe, it looks like the steppe migrants were largely young, male and violent. A study by Martin Richards at the University of Huddersfield, UK, and his colleagues found that maternally inherited mitochondrial DNA sequences changed relatively little when they arrived. By contrast, between 60 and 90 per cent of men now living in the area can trace their paternally inherited Y chromosome to Yamnaya-related migrants.

“Indigenous males seem to have been marginalised by the new arrivals much more than the women and were unable to have children to the same extent,” says Richards. “This seems unlikely to have been a wholly benign process.”