February 28, 2012 | 2
Ever since two hikers happened upon the mummified body of Ötzi the Iceman on a high mountain pass in the Ötzal Alps in 1991, scientists have been working to figure out who he was and where he came from. Previous research indicated that Ötzi spent his life within a 60-kilometer radius of where the hikers found him and died around 5,300 years ago, most likely from an arrow wound in his shoulder. Now the sequencing of his genome is allowing experts to fill in more details, such as the color of his eyes, his cardiovascular health and where his ancestors originated.
Albert Zink of the European Academy of Bozen/Bolzano in Italy and his colleagues report the results of the sequencing work in a paper published today in Nature Communications (Scientific American is part of Nature Publishing Group). The team found that the Iceman probably had brown eyes and type O blood. He was also most likely lactose intolerant as an adult. Analyses further revealed that the Iceman had several genetic risk factors for coronary heart disease. Several years ago, computer tomography scans of the mummy showed evidence of arteriosclerosis—hardening of the arteries—yet he appeared to have a healthy lifestyle. The new work suggests that a genetic predisposition to heart disease might explain the arteriosclerosis visible in the CT scans. Cardiovascular disease may not have been the Iceman’s only health issue. The investigators also found traces of DNA from the bacterial pathogen Borrelia burgdorferi, which causes Lyme disease in humans—the oldest such case on record.
Intriguingly, comparison of the Iceman’s genome with DNA from present-day populations linked him not to mainland European groups, but to people from the Mediterranean island of Sardinia. Study co-author Peter Underhill of Stanford University observes that there are two possibilities for how someone with a Sardinian genetic signature ended up in the Alps 5,300 years ago. ”The presence of similar genetic heritage to [the] Iceman persisting in modern day Sardinians is suggestive that Sardinia represents a relic distribution of the gene pool that was in place on the Italian mainland during prehistoric times but now has largely been transformed by subsequent population events such as migrations, genetic mixing, etc.,” he offers. “Sometime during the past [10,000] years some people with a genetic constitution similar to [the] Iceman’s colonized Sardinia. This isolated region/gene pool was more impervious to events that transpired on the mainland.” Alternatively, Underhill notes, the Iceman’s parents may have have traveled to the mainland from Sardinia. Archaeologists have found volcanic glass (obsidian) on the mainland that originated from Mt. Arci on Sardinia, indicating that trade existed between Sardinia and the mainland. Perhaps the Iceman’s parents were involved in that trade, Underhill speculates.*
“Further ancient DNA analyses from these regions will be necessary to fully understand the genetic structure of ancient Alpine communities and migration patterns between the insular and mainland Mediterranean,” the researchers conclude.
*Post updated at 12:16 p.m. to include comments from Underhill.
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