Researchers have detected a familiar pathogen in 5,300-year-old ice mummy Ötzi, raising speculations that the iceman had suffered from a stomach bug when he had been murdered. How does this hint at waves of human migration that are previously unknown?
A paper published in the journal Science on Jan. 7 found that Ötzi was infected with Helicobacter pylori, which also currently affects humans.
H. pylori bacteria are carried by about half of all modern humans and causes ulcers and stomach cancer in a small population.
The iceman’s corpse was uncovered in 1991 by backpackers in Italy’s Tyrolean Alps, sheathed in ice at an altitude exceeding 3,000 meters. He is believed to have died from an arrow shot in the back, but studies also revealed that he suffered from cavities, hardened arteries and a range of other health issues.
Familiar Stomach Bug In The Ancient Iceman
Back in 2010, researchers examining Ötzi's CT scan noticed that his stomach had been preserved, revealing that his last meal included ibex and wild grains.
A team of researchers led by biomolecular archaeologist Albert Zink in Bolzano, Italy, further decided to probe the iceman's stomach and gut.
In what was left of his digestive tract, the team found DNA from H. pylori, whose pattern of age-induced damage showed that the bacteria colonized the living Ötzi rather than his corpse.
Too bad for Ötzi, the strain he carried was not the normally harmless one, but a type of H. pylori linked to abdominal inflammation and stomach disorders found in modern humans.
Zink and his team used purification techniques to obtain genetic material from the iceman's stomach and discovered that it matched 92 percent of the modern bacterium's genome containing 1.6 million letters.
The H. pylori bacterium in the iceman's stomach was found to have cellular toxin-producing genes which enable the modern bacterium to cause ulcers. The finding also showed that the iceman's stomach contains protein fragments similar to those seen in inflamed stomach tissues of infected people.
Yoshan Moodley, study co-author and geneticist at the University of Venda in South Africa, said this bacterium was likely the original strain that resided in the stomach of the first Europeans.
"This ancient HP strain has allowed us what is perhaps a unique opportunity to discover what populations of Helicobacter pylori existed in Europe during this copper age," he explained.
Evolutionary And Migratory Cues
Ötzi's well-preserved corpse provides a window to ancient life.
Previous research has confirmed, for instance, that he was of European descent, with his closest kin now living in Sardinia and Corsica. He had brown hair and brown eyes, and the copper in his hair suggests that he might have worked in a metal or weapons production involving the use of copper.
More importantly, the latest find may have solved a crucial question about the evolutionary movement of the H. pylori strain.
Based on DNA amplification and targeted genome capture, scientists identified Ötzi's H. pylori infection as a certain Asian strain, which has only been detected three times in modern Europeans.
This finding is the first proof that the strain had already inhabited Central Europe during the Copper Age, or from the fifth and third millennia BC.
As the infection is more closely associated with Asian strains than with Asian-African hybrid strains existing today, the results suggested that Asian and African strains had yet to mix during the iceman’s lifespan.
“We can say now that the waves of migration bringing African H. pylori into Europe had not occurred in earnest by the time the Iceman was around,” said Moodley, adding that the bacterium DNA in the wonderfully preserved specimen may not be extracted again elsewhere.
The discovery is only a single sample detected in Ötzi, but it may be a piece of the complicated puzzle of research on other mummies worldwide.
This does not involve ancient Egyptian mummies, though, as their stomachs are removed during mummification.