An analysis of the stomach contents from a 5,300-year-old European mummy known as Ötzi the Iceman has turned up a double surprise, scientists say.
First, the researchers found DNA traces of a nasty strain of bacteria, Helicobacter pylori, which is linked to ulcers. That discovery, paired with the presence of other immune-system proteins, suggests that the Iceman could have been suffering from stomach problems in addition to his other maladies – ranging from hardening of the arteries and lactose intolerance to Lyme disease and bad teeth.
The second surprise came when the research team looked more closely at the bacteria’s genome. The DNA sequence showed that the bacterial strain wasn’t the one that’s most common in Europeans today, but is linked instead to modern-day populations in South Asia.
That finding appears to answer questions relating to the peopling of Europe thousands of years ago, the researchers report in this week’s issue of the journal Science.
“This one genome has put things into wonderful perspective for us,” said Yoshan Moodley, a geneticist who’s based at the University of Venda in South Africa and the University of Veterinary Medicine in Vienna.
The Iceman may have had a hard life, but when hikers found his frozen mummy in the Italian Alps glacier in 1991, it was a godsend for scientists seeking to reconstruct the lifestyle of Europeans in the Copper Age. Forensic studies determined that the Iceman was a 45-year-old hunter who was apparently murdered on the trail, with the fatal arrowhead lodged in his left shoulder.
In 2010, the Iceman was defrosted long enough for scientists to take samples for genetic analysis. The stomach wasn’t well-preserved enough for study, but geneticists could analyze the contents of the stomach. That’s how they determined that the Iceman ate ibex meat shortly before he died. And that’s how they found the H. pylori bacteria.
H. pylori is widely found in low-income populations around the world, but different strains predominate in different regions. The strains that are prevalent in modern-day Europe share a high level of ancestry with strains found in North African populations. In contrast, the strain in the Iceman’s remains showed only a tiny trace of that ancestry, with a much stronger link to strains that have been traced to India and other parts of South Asia.
That doesn’t mean the Iceman came from India. But it does indicate that the North African strain proliferated in Europe sometime after the Iceman died. That’s consistent with the view that a wave of migrants swept into Europe around 5,000 years ago, bringing an agricultural way of life (and their gut bacteria) with them.
“It could fit very well,” Moodley said.
Because of the poor preservation of the stomach, scientists can’t say whether the Iceman actually had an ulcer when he died. However, an analysis of the proteins that were left behind suggest that his immune system was responding to gastric inflammation.
Only humans are known to harbor H. pylori. That means the bacteria could serve as a genetic marker for human migration, not only for Europeans but for other populations around the world.
“One thing we definitely want to do is to extend our investigation also to other mummies, because we could show how it works and that we are able to reconstruct H. pylori from stomach material,” said study co-author Albert Zink, a paleopathologist from the European Academy of Bozen/Bolzano in Italy. That’s the institute where the Iceman is currently being kept on ice.
Zink said he and his colleagues are already in touch with fellow researchers who have access to mummies in South America, South Korea and Northern Europe. But what about Egyptian mummies? Unfortunately, they’re not good candidates for the studies that Zink has in mind. “There, the stomach was removed during the mummification process,” he said.
The corresponding authors of the Science study, “The 5,300-Year-Old Helicobacter Pylori Genome of the Iceman,” are Frank Maixner and Albert Zink of the Institute for Mummies and the Iceman at the European Academy of Bozen/Bolzano. Moodley and 20 other researchers are co-authors.