科学美国人60秒:Iceman ?tzi Died with a Bellyache

Otzi—or as he’s also known, the Iceman—was discovered frozen in the Alps in 1991 by two German tourists. The 5,300-year-old body has been analyzed in various ways and been the subject of numerous scientific publications. And now it’s been looked at again. Because scientists realized that the contents of the Iceman’s stomach were still intact. Which gave them the chance to look for evidence of the common stomach bacteria Helicobacter pylori, or H. pylori. What they found tells us more about Otzi—and more about how Otzi’s ancestors came to Europe. The study is in the journal Science. [Frank Maixner et al, The 5,300-year-old Helicobacter pylori genome of the Iceman]

The researchers were able to extract genes from H. pylori in the stomach to produce the oldest known genome sequence of a pathogen. The Iceman seems to have been infected with a virulent strain. So in his last days on Earth, Otzi probably had one bad bellyache.

“The strain had already reacted with the Iceman's immune system. This we could show. So we showed the presence of marker proteins which we see today in patients infected with Helicobacter.” The University of Vienna’s Frank Maixner.

It’s estimated that more than half the world’s human population harbors various strains of the ulcer-causing bacteria. And different strains are associated with different places on the globe.

“We use then Helicobacter as a surrogate for what humans were doing at various stages of our prehistory.” Yoshan Moodley from South Africa’s University of Venda.

Europeans today mostly harbor H. pylori that’s a mix of Indian and North African strains. But Otzi’s bacteria matched only the Indian variant.

“This one genome has put things into wonderful perspective for us, answered this question that we've been trying to answer for years. We can say now that the waves of migration that brought these African Helicobacter pylori into Europe had not occurred or at least not occurred in earnest by the time the Ice Man was around.”
 

That finding does not mean that North Africans themselves migrated into Europe after the time of the Iceman. The new strain may have evolved in the Middle East and then been introduced by later waves of farmers migrating out of the Fertile Crescent. More clues into human migration from H. pylori genes may be forthcoming. Just as soon as we find more perfectly preserved stomachs in long-frozen bodies.

—Cynthia Graber