Few of our ancestors have been so thoroughly poked and prodded as Neolithic Tyrolean Iceman "Ötzi," discovered melting out of an Alpine glacier in 1991. Researchers have probed his stomach and bowels for traces of his last meal and analyzed his teeth for cavities. Now, an international team has sequenced his entire genome, and it turns out Ötzi still has some surprises in store.
Earlier computer scans had revealed Ötzi's severe arteriosclerosis, or hardening of the arteries. But the new analysis shows that Ötzi had a genetic predisposition to the condition, despite the fact that as a hunter-gatherer he had none of what are currently believed to be the relevant risk factors, such as being overweight, getting too little exercise, and smoking or drinking. "This new data suggests that we might be less able to prevent arteriosclerosis than we believed," notes cardiologist and mummy expert Gregory Thomas of the University of California, Irvine, who was not involved in the new work.
The whole genome sequencing also reveals more about Ötzi's ancestors. Earlier research analyzed Ötzi's mitochondrial DNA, which is inherited through only the female line, but had found few known matches among modern populations. Now sequencing of his Y chromosome places him in the rare G2A4 haplogroup, meaning that his paternal genes are linked to a population that left the Near East for Europe at the beginning of the Neolithic era, roughly 1000 years before Ötzi himself lived.
Ötzi's genetic profile marks him as being most closely related to small populations currently living in the islands of Sardinia and Corsica, as well as some of the more remote areas of Georgia and Russia, says geneticist Angela Graefen of the Institute for Mummies and the Iceman in Bolzano, Italy, one of the principal researchers on the paper. That doesn't mean that Ötzi was Sardinian or Corsican, Graefen notes, but that those populations may be the closest living genetic matches to the hunter-gatherers who originally migrated into Europe.
The genome analysis, published this week in Nature Communications, also helps flesh out our picture of Ötzi the man: Researchers now know he had brown eyes, brown hair, type-O blood, and shared the lactose intolerance that was then still the norm among Neolithic Europeans. He was also the first known carrier of Lyme disease: the sequencing yielded genes from the disease-causing Borrelia burgdorferi bacterium. Although scientists can't know whether Lyme disease actually made Ötzi sick during his lifetime, the discovery of 60% of a B. burgdorferi genome from a Neolithic carrier shows that this pathogen has plagued humans for thousands of years. Until researchers compare the B. burgdorferi genome from Ötzi with more modern incarnations of the pathogen, they won't have a clear picture of how Lyme disease evolves. "But depending on the research other scientists are doing over the next few years, we could be gaining a lot more insights from Ötzi's genome," Graefen says.
The new paper adds to our knowledge of Neolithic life, says mummy expert Frank Ruehli of the University of Zurich in Switzerland. "Of course Ötzi is only one individual, but he's a very well-preserved, well-described individual, whom we have a lot of additional information about already. So this is an important step."