From the stomach and intestines of a famous copper age mummy, scientists have recovered the oldest complete pathogen genome on Earth. The mummy is none other than Ötzi the Iceman, whose frozen 5,300-year-old body was discovered in 1991 in the glacial Alps of Italy.

The authors of a study published on Jan. 8 in the journal Science found the gram-negative bacteria Helicobacter pylori in all twelve of the biopsy samples they took from Ötzi the Iceman’s gastrointestinal tract.

The genome of Ötzi’s H. pylori has a 92.2 percent match to modern H. pylori, which afflicts around half of the human population and can cause ulcers and stomach cancer.

In addition, the researchers found fragments of inflammatory response proteins in Ötzi’s stomach, as well as toxin-coding genes in the genome of H. pylori. These finds indicate that H. pylori may have caused Ötzi illness.

However, it is unlikely that the bacteria, or the various other health issues that Ötzi suffered from, ultimately caused the 40-to-50-year-old iceman’s death. Ötzi is believed to have been killed by an arrow in his left shoulder.

But the discovery of ancient H. pylori reveals more than the tenacity of stomach bacteria. H. pylori relies on humans to survive and passes through close contact, which typically occurs only in families. Thus, the presence of H. pylori in Ötzi’s body can provide clues about how humans migrated thousands of years ago.

Today, Europe hosts a hybrid version of the two original varieties of H. pylori: the Asian strain and the African strain. Past research has suggested that this modern H. pylori emerged in the Middle East 50,000 years ago, after the last glacial maximum, as a result of human migration.

Interestingly, Ötzi’s bacteria, which is 5,300 years old, matches the Asian strain of H. pylori, not the modern European version as the earlier theory would predict. Did prehistoric humans migrate to Europe later than previously thought? Did two strains of H. pylori exist in Europe at the same time?

More and more evidence is implying that multiple waves of migration occurred. Even if we never figure out how humans first migrated to Europe, Ötzi provides a one-of-a-kind chance to explore the mystery.

Yoshan Moodley, a geneticist at the University of Venda in South Africa and one of the authors of the study, explains in Scientific American: “This might never happen again that we find such a wonderfully preserved specimen where Helicobacter pylori DNA still can be extracted.”