冰人的DNA解码

Ötzi, the Tyrolean iceman frozen in a glacier for 5300 years until his1991 discovery, was brown-eyed, prone to heart disease, lactose intolerant, blood group O and infected with lyme disease, a new analysis of his DNA has revealed.

Writing inNature Communications, Saarland University scientist Andreas Keller and his colleagues used a 0.1 gram bone sample collected from the iceman's pelvis to extract DNA and, for the first time, read the full genetic code of this mummified man who was born in 3300 BC near what is now Feldthurns in Italy and who died, aged about 45, with an arrowhead embedded in his left shoulder.

The incredible level of preservation of Otzi, owing to his having become rapidly frozen after he died, and the fact that most of his clothes and the possessions he was carrying have survived with him, means that he offers an unprecedented window into lives of early European inhabitants.

Decoding his genome has therefore been a high priority in order to understand how he "fits into" the genetic jigsaw of human history, both locally and globally. However, until now, genetic techniques haven't been able to overcome the fragmentation and deterioration of the genetic material sustained during the 5000 years that the iceman lay in his 3000 metre-high final resting place.

To succeed in this feat, Keller and his colleagues used a computer system to work out how more than a billion short DNA sequences overlapped with each other in order to piece Otzi's genome back together.

Although the analysis of the code is only just beginning, some tantalising details are already beginning to emerge. The iceman more than likely had brown eyes, the team have found. He also had a gene that would have boosted his risk of vascular disease by 40%, which fits with the calcifications in the walls of his arteries revealed by CT scans of the body.

His MCM6 gene, which encodes lactase, the enzyme that breaks down milk, reveals that Otzi would have been lactose intolerant, and his closest descendents are Europeans living in Corsica and Sardinia.

In an added twist, the team also flushed out the DNA signature ofBorrelia burgdoferi, the tick-borne bacterium that causes Lyme disease, making Otzi also the world's first confirmed Lyme's sufferer!