Wracked by arthritis, bitten by ticks, and murdered atop an icy mountain 5,300 years ago, Otzi the “Iceman” also carried ulcer-causing bacteria, scientists reported on Thursday.
The Heliobacter pylori bacteria was retrieved from the mummified stomach of the ancient 40-year-old man killed by an arrow wound and frozen in the Alps, who was uncovered by hikers in 1991. H. pylori is now the oldest microbe to be genetically mapped.
Otzi has been studied for two decades for insight into early Europeans — he died wearing elaborate fur clothing, armed with a copper axe, and covered with 61 tattoos (making him the oldest known tattooed man). Now researchers are examining his gut microbes, or microbiome, for more clues to the life and death of the Iceman.
“He had a very rough life,” study lead author Frank Maixner of the European Academy of Bozen/Bolzano in Italy told reporters at a telephone briefing. “We cannot be 100% certain he suffered gastric distress but we can say his immune system was reacting to the bacteria.”
Today, roughly half of all people worldwide are infected by H. pylori, which lives in the acidic human stomach and about 10% of the time causes ulcers. Varied strains of the bacteria are tied to populations across the world, with modern-day Europeans afflicted by a unique one that appears to be a mixture of older African and Asian ones.
But not Otzi, according to the new study, published in the journal Science. The complete genetic map, or genome, of the H. pylori bacteria found in his frozen stomach shows it belongs to an Asian strain of bacteria now largely confined to the guts of people living in northern India.
That suggests the north Indian strain once belonged to most prehistoric Europeans, prior to an influx of farmers from the Middle East into the continent more than 4,000 years ago. Those new arrivals likely carried the African H. pylori strain that mixed with the older Asian one to produce today’s signature European H. pylori bugs.
“To actually sequence the genome of a pathogen this old is a dream come true,” ancient microbe expert Gary Toranzos-Soria of the University of Puerto Rico, who was not involved in the new study, told BuzzFeed News. “The beautiful thing is the paper sheds light on one hypothesis about ancient human migration, which is wonderful.”
While studies of human gut microbes, the microbiome, have run rampant in the last decade, the field of paleomicrobiology is only blooming now with the Otzi study, Torzanos-Soria added. “The microbiome is absolutely essential to what makes us human, we couldn’t survive without these microbes,” he said. “So to glimpse what they looked like a long time ago is really important.”
To sequence the genes of the ancient gut bugs, the researchers first retrieved samples of Otzi’s stomach lining and the much-studied contents of his stomach, which previous researchers had shown contained last meals of goat, deer, and bread. Mixed in were DNA segments from H. pylori bacteria, which the team painstakingly knitted into a complete genetic map of the bugs.
Poor preservation of Otzi’s stomach lining means the researchers couldn’t tell whether he suffered from ulcers. However, the scientists did find proteins expressed by the human immune system in reaction to an H. pylori infection. “He probably had some stomach issues,” Maixner said.
H. pylori is probably as old as our species, Homo sapiens, perhaps dating back to 116,000 years ago. (And around 50,000 years ago, lions appear to have captured their own strain of the ulcer-causing bacteria by eating people.) Carried out of Africa by human migrations around 60,000 years ago, today’s Northern Indian strain of H. pylori may reflect an ancient lineage of stomach bugs. In Northeast Africa a newer strain evolved within the last 52,000 years, to later mix with the bugs today giving ulcers to people across Europe.
“A real, but unintended, message here is that Europe has been the destination of many a migrant,” study author Yoshan Moodley of South Africa’s University of Venda told BuzzFeed News by email. “And that migration into and away from any place in the world is as old as mankind.”