The key finding on ancestry was both precise and striking: the new high-coverage, low-contamination genome showed no detectable Steppe Herder ancestry. The apparent Steppe signal from the 2012 study vanished when the contamination-corrected data was used. This was not a marginal revision; the steppe ancestry that had been reported and discussed in the previous literature was an artifact of the contamination problem.
What replaced it was an unusually high proportion of Anatolian early farmer ancestry. Using a statistical method (qpAdm) for decomposing ancestry into components, the team estimated Ötzi’s farmer-related ancestry at approximately 90 percent (± 2.5 percent), with roughly 10 percent Western Hunter-Gatherer ancestry. Some accounts of the study reported this figure as more than 92 percent, reflecting how figures were described in press releases rather than the paper’s specific statistical estimates — the paper gives 90 percent ± 2.5 percent as the qpAdm result, with related analysis by RFMix yielding approximately 8.6 percent hunter-gatherer ancestry.
For context: among hundreds of ancient European genomes from roughly the same period, Ötzi and an ancient individual from a northern Italian site called Italy_Broion_CA.SG had the highest farmer-related ancestry proportions documented. Ancient Sardinians from the same period showed Anatolian farmer ancestry as high as roughly 85 percent. Spanish and Sardinian individuals from the fourth millennium BCE ranged from about 27 percent to 87 percent in farmer-related ancestry. Ötzi’s value was at or above the high end of this distribution.
The interpretation the researchers offered was population structure: the Alpine region, specifically the valleys on the southern side of the Alps, may have been relatively isolated from the population mixing that was occurring in lowland Europe at the time. The Alps could have served as a geographical and cultural barrier to gene flow, allowing a community with predominantly Anatolian farmer ancestry to persist without the high rates of hunter-gatherer admixture that characterized northern and western European populations of the same period.