The puzzle of how we got here appears to have a few more clues, after scientists discovered an ancient strain of gut bacteria in a 5,300-year-old 'Iceman' mummy.
According to researchers, the older strain of Helicobacter pylori (H.pylori) bacteria is quite similar to a modern strain found in Asia.
This suggests that early European farmers may have had contact with Asians before they migrated to Europe.
“It provides almost literally a mirror image of human population structure,” said Yoshan Moodley, an author of the paper told ABC News.
Published in Science, the paper suggests Ötzi the “Iceman's” ancestors inherited the pathogen from Asia and not Africa.
Today, the bacteria is found in around half the world’s human population, causing stomach ulcers and cancer in less than 10 percent of those who carry it.
When researchers sequenced the genome from Ötzi's gut bacteria, they found it closely resembled strains found in Asia rather than those found in modern Europe or Africa.
Comparatively, today's European strain has more DNA from the African version of H.pylori, which has lead scientists to propose a new theory about human migration.
Lead author, Frank Maixner, of the paper told Science:
The ancestors of early European farmers such as Ötzi must have carried H. pylori with DNA from Asian strains perhaps in the Middle East before they migrated to Europe. Then, new immigrants carrying African microbes arrived in Europe much later, after Ötzi lived. The two types of microbes mixed in these migrants, creating today’s European strain much more recently than expected.