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New High-Coverage Ötzi Genome Points to High Level of Anatolian Ancestry

NEW YORK — With a new high-coverage genome, researchers have found that the nearly 5,300-year-old mummified Tyrolean iceman, known as Ötzi, has more Anatolian farmer-related ancestry than previously expected.

Ötzi's remains were found in the Italian part of the Ötztal Alps in 1991, and radiocarbon dating and stable isotope analysis indicated that he lived during the Copper Age.

In a paper published in Cell Genomics on Wednesday, an international team led by investigators at the Max Planck Institute for Evolutionary Anthropology reported that Ötzi was likely bald, dark-skinned, predisposed to diabetes and obesity, and had an unusually high amount of Anatolian-farmer-related ancestry.

These results differed from a 2012 study, in which researchers had used the ABI SOLiD sequencer platform to generate a low-coverage version of the iceman's genome. That study suggested that Ötzi had traces of Steppe herder ancestry, a mildly dark skin tone, and a head full of hair. The results, however, were likely due to contamination, the new study's authors noted.

In this new study, the investigators used Illumina sequencing to produce a new high-coverage, 15.33X, genome from two samples from the iliac bone, like in the 2012 study. However, there was almost no contamination in the samples this time around.

Since the previous study, not only have sequencing technologies advanced tremendously, but many more genomes of other prehistoric Europeans have been fully decoded, often from skeletal remains, which proved instrumental for the new analysis, according to Max Planck.

Through an ancestry analysis, they found that Ötzi had a high proportion of genes in common with those of early farmers from Anatolia and found no traces of Steppe herder ancestry.

The genetic makeup of most present-day Europeans is mainly from the admixture of three ancestral groups: western hunter-gatherers who gradually merged with early farmers who migrated from Anatolia about 8,000 years before; they were later joined by Steppe herders from Eastern Europe.

The researchers' analysis found that Ötzi and his relatives came from a relatively isolated population with little contact with other European groups. This suggests they were cut off from other European individuals that mixed with ancient hunter-gatherers.

By analyzing various SNPs associated with physical appearance and metabolism, the researchers sought to gain insight into Ötzi's lifestyle and appearance.

Ötzi harbored variants thought to be related to adaptations of a farmer's lifestyle. In particular, the researchers predicted that the iceman likely had an agricultural diet and intermediate levels of high-density lipoprotein cholesterol.

Meanwhile, this trait analysis also suggested Ötzi was bald with a darker skin tone than previously thought, a finding they based on the analysis of 170 skin pigmentation-associated SNPs that had been identified in the UK Biobank. "It's the darkest skin tone that has been recorded in contemporary European individuals," anthropologist Albert Zink, study coauthor and head of the Eurac Research Institute for Mummy Studies in Bolzano, Italy, said in a statement.

While it was previously thought that the mummy's skin had darkened during its preservation in the ice, this study indicates that Ötzi had a dark skin complexion during his lifetime. The authors corroborated this finding with previous histological analysis of the iceman's skin.

They cautioned, though, that phenotypes are a combined effect of genetic mechanisms and environmental exposures, and multiple SNPs could be responsible for the heritability of complex traits like male-pattern baldness and skin pigmentation.

Despite the new findings, the authors highlighted several limitations of the study. Since they only analyzed the DNA of a single person, the results offer a narrow picture of the population history of Ötzi's time and region. "Future studies with a denser sampling from the southern Alps will be needed to replicate our findings and show if the iceman was an outlier or a representative of his population," the authors wrote.