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The Iceman Is All Italian

30 October 2003 (All day)
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The renowned Alpine Iceman, known as Ötzi, has painted an extraordinarily detailed picture of life some 5000 years ago, during the late Neolithic era. Researchers know Ötzi's age, his health, what he ate, and how he died. Now they have pinpointed his origins to a few valleys in southern Tyrol. Ötzi probably never strayed more than 60 kilometers from his birthplace and spent his entire life in the mountains of what's now Italy.

To link Ötzi to particular places, the researchers followed a number of clues. Wolfgang Müller of Australian National University in Canberra and an international team studied Ötzi's tooth enamel and thighbone. Dental enamel is fixed at the time the tooth is formed, so the three teeth the scientists examined contain the signature of trace elements in food ingested when Ötzi was about 3 to 5 years old, Müller explains. Bone, however, is remineralized with ingested substances every 10 to 20 years, giving a clue to the Iceman's whereabouts in adulthood. And tiny pieces of mica in Ötzi's intestine yielded data about the hours just before his death.

The isotopic signatures of tissue samples could then be matched to various soil and water samples from across the region. For example, ratios of the stable isotopes of oxygen in rainfall vary with altitude and geography. High-altitude inland areas, such as those north of where Ötzi was found, are depleted in the heavier oxygen isotope (18O), which drops out first as clouds travel from the Atlantic Ocean. More southern, Mediterranean-fed rainfall carries higher levels of 18O, and Ötzi's teeth matched these southern values, indicating that he lived in those valleys when his teeth formed. But his thighbone values lay between those and the values from the area where he was found, indicating that as an adult he spent time farther north at a higher altitude than his native valley.

In addition, the Alpine mountains around the Iceman are so geologically complex that they include at least four rock types, each of which has a distinct ratio of radioactive isotopes of strontium and lead. Because food reflects the isotopic composition of the soil in which it was grown, the team could narrow Ötzi's childhood origins down to several southern valleys. Putting together these two types of isotope data, the researchers have zeroed in on the Eisack Valley as a good candidate for his childhood home.

Finally, the researchers characterized Ötzi's later stomping grounds with argon-argon dating of 12 tiny pieces of white mica that may have come from the grindstone of the grain--wheat and barley--he had eaten shortly before his death. The age distribution of the mica pieces--between 95 million and 300 million years--is consistent with that of a small area west of the Eisack Valley, called lower Vinschgau. Thus Müller's group concludes that Ötzi grew up in the Eisack Valley, then as an adult spent time in the mountains of lower Vinschgau before setting off on his final journey to the Ötz valley. They report their findings in the 31 October issue of Science.

"It's a marvelous paper," says Henry Schwarcz, a geologist at McMaster University in Hamilton, Ontario. "This multidisciplinary approach simply hasn't been done in other sites." However, Jurian Hoogewerff of the Institute of Food Research in Norwich, U.K., questions the conclusions drawn from the oxygen isotopes. He wonders whether the north-south variation seen today existed 5000 years ago. He found no such variation in a 2001 study of medieval Tyrolean skulls.

Related site
Ötzi's home, the South Tyrol Museum of Archaeology

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