A new genetic analysis has changed our understanding of 脰tzi, the mummified 鈥淚ceman鈥� who lived 5300 years ago and was found in a glacier in the Alps.
The findings reveal that almost all of 脰tzi鈥檚 DNA was inherited from early farmers, who moved into Europe a few thousand years before he was born.
The genome also indicates that he had darker skin than any people with predominantly European ancestry today, and may well have been bald.
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脰tzi鈥檚 mummified body was discovered in 1991, thawing out of an Alpine glacier near the border of Austria and Italy. He is estimated to have lived between 3350 and 3120 BC. The remains have been studied for more than 30 years, revealing, among other things, that he had a wound from an arrow, suggesting he was murdered.
In 2012, a draft of 脰tzi鈥檚 genome was . It suggested he had ancestry from three different groups: hunter-gatherers who first moved into Europe around 40,000 years ago, early farmers who arrived from the Middle East around 9000 years ago, and people from the Eurasian steppes who arrived after 5000 years ago.
鈥淭hat was always weird,鈥� says at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. The steppe peoples didn鈥檛 arrive in Europe until after 脰tzi died, so it didn鈥檛 make sense that he had steppe DNA. Many geneticists suspected that the genome had been contaminated with modern European DNA, which contains steppe DNA.
To find out, Krause and his colleagues have re-sequenced 脰tzi鈥檚 genome using modern techniques. The new genome is much more accurate, and shows no sign of steppe ancestry. 鈥淭here was almost 10 per cent contamination in the old dataset,鈥� says Krause. Albert Zink at Eurac Research in Bolzano, Italy, who worked on both the 2012 study and the new study, agreed that there was some human contamination in the original genome.
It turns out that about 90 per cent of 脰tzi鈥檚 ancestry came from the Middle Eastern farmers, with the remainder from the hunter-gatherers. This is unusual: most people living in Europe at that time had a more mixed ancestry, because the incoming farmers interbred with the hunter-gatherers.
鈥淣ow he鈥檚 an outlier in another way,鈥� says Krause. 鈥淗e has a lot of early farmer ancestry, more than anyone else from this time period.鈥� It could be that 脰tzi himself was unusual in this way, or that his population didn鈥檛 mix much with hunter-gatherers when they entered Europe 鈥� perhaps because they lived in relatively remote areas of the Alps.
The new genome reveals a gene variant that is associated with a higher risk of male pattern baldness. This makes sense, says Krause, because very little hair was preserved with 脰tzi. 鈥淗e was in his late 40s so I think it鈥檚 possible [he was bald],鈥� he says.
Krause and his team also identified 154 sites in the genome that have been associated with in modern populations. The sequences they found suggest that 脰tzi鈥檚 was darker than that of people with predominantly European ancestry living today, though not as dark as that of people from sub-Saharan Africa.
This fits with an emerging body of evidence about prehistoric Europeans, says , also at the Max Planck Institute for Evolutionary Anthropology, who wasn鈥檛 involved in the study. 鈥淭he hunter-gatherers most likely had even darker skin, and also probably the early farmers would have had darker skin than what we know from Europe today,鈥� she says.
鈥淭he light pigmentation Europeans have today is a very recent phenomenon,鈥� says Krause. It 鈥渞eally only was established as light as it is today about 4000 years ago鈥�. Compared with hunter-gatherers, farmers ate less meat and fish, putting them at risk of vitamin D deficiency: losing their skin pigmentation enabled them to synthesise more vitamin D in their skin. 鈥淚t鈥檚 one of the strongest selective signals we have in the human gene pool,鈥� says Krause.
Early investigations of 脰tzi鈥檚 body in the 1990s found evidence of melanin pigment in his skin, says Krause, suggesting he had dark skin pigmentation. Nevertheless, most reconstructions portrayed him as having light pigmentation.
鈥淚t used to be that you would depict ancient Europeans similar to modern Europeans, but that doesn鈥檛 actually have to be the case at all,鈥� says Mittnik.
Cell Genomics
