Early Europeans drank cow's milk for thousands of years before becoming adults and evolving the ability to fully digest it, scientists say.
New results published in the journal Nature suggest that being able to digest lactose in milk was usually not a great advantage for ancient peoples in Europe. Instead, new research suggests that famine and disease made lactose intolerance fatal. It challenges long-held hypotheses that dairy farming spread among ancient populations, with genetic specificities that prevent
Human children, like other young mammals, produce an enzyme called lactase that breaks down lactose. The lactase gene is normally turned off in adults. This is because, with the exception of humans, adult mammals do not drink cow's milk.
Without lactase, lactose from milk feeds gas-producing gut microbes and can cause unpleasant digestive problems. You'll have some diarrhea, you might fart a little more, and that might be uncomfortable for you," says Mark Thomas, a geneticist at University College London, who led the genetics study of the new study.
But when our ancient ancestors suffered from pestilence and famine, drinking milk Getting diarrhea was probably more than just uncomfortable, the authors suggest.
About a third of people alive today carry a genetic mutation that prevents the lactase gene from being turned off. This trait has evolved independently many times in the ancestors of people now living in Africa, the Middle East, South Asia, and parts of Europe.
Scientists have long believed that lactase persistence evolved with the spread of dairy farming. This happened over thousands of years, starting around 7000 BC.
However, previous studies found little persistence of lactase in Europe until about 3,000 years ago. However, it took only a few thousand years for this trait to spread, a blink of an eye in the process of evolution.
Why this trait evolves so rapidly has been a mystery.
"The persistence of lactase, from the last 8,000 to 10,000 years he has been under an enormous amount of natural selection...more than any other part of the European genome." said Thomas. "It was, for a very long time, the only trait where life and death were affected more than any other trait. …That's insane. It just defies explanation." In their quest, the authors sought to reconstruct the history of milk use in the region over the past 9,000 years. They examined the fat residue left on more than 7,000 of his pottery shards collected at 550 archaeological sites across Europe.
"When people cook, the fat liquefies and seeps into the pores of the ceramic," says organic geochemist and study co-author Melanie Roffe of the University of Bristol. Sark said. "It's amazing, really. But thousands of years later, when archaeologists unearth discarded pottery and analyze the pottery, it's still there."
, indicating that milk consumption was widespread in most of Europe for thousands of years before Europeans became lactose-tolerant. The researchers found no evidence that drinking cow's milk is detrimental to the health of modern adults who do not produce lactase. Using data on ancient demographics to approximate how people coped with disease and disease, the researchers found that the evolution of lactase persistence could be better explained than milk consumption.
Famine may have forced ancient peoples to drink more milk than usual, as other food sources became scarce. And both malnutrition and disease may have made lactose-induced diarrhea so dangerous: Severe diarrhea can be fatal — her cause of death for children under five worldwide 2nd place.
Shevan Wilkin, a biomolecular archaeologist at the University of Zurich who reviewed the new paper, said the study was an important step forward, but that famine and disease alone could explain the evolution of lactase persistence.
"The reason I don't know if they think they're right, and I don't know if they think they're wrong, is that 2,000 years ago there was definitely a time of famine." because there was," said Wilkin.
Thomas said he hopes similar studies will be done in Africa, where lactase persistence has evolved independently three times. It has been overstudied and future research should focus on other regions, including Central Asia.
"It would be very interesting if this could be applied to multiple locations." ', said Wilkin. "This is a very cool and ambitious undertaking, and I think it will spur a lot of new research."
