The steppe ancestry in his genome didn’t fit the timeline of documented population movements.

He was too old to have that ancestry by the standards of every other ancient European sample available for comparison.

The explanation for the anomaly emerged when the 2023 team examined the original data more carefully.

The 2012 genome had been produced using sequencing technology of that era, which was considerably less powerful than what became available in the intervening decade.

The original sample had been contaminated with modern human DNA — and that modern DNA, from people working with the samples, had introduced steppe-ancestry genetic material that was not Ötzi’s own.