People who can tolerate milk get the extra calories and protein and pass their genes on to offspring who are healthier than those who don’t have the trait – a condition known as lactase persistence. To digest the sugars in milk during adolescence.
But a new study has offered an entirely different theory, arguing that side effects like gas, bloating and intestinal cramps aren’t enough to move the evolutionary needle on genetic modification.
“Prehistoric people in Europe may have started consuming milk from domesticated animals thousands of years before they developed the digestive gene,” the study’s authors said.
The thesis, published in the journal Nature, developed in collaboration with more than 100 scientists in a variety of fields including genetics, archeology and epidemiology. Scientists mapped estimated milk consumption in Europe from about 9,000 years ago to 500 years ago.
By analyzing animal fat residues on pottery from hundreds of archaeological sites, along with DNA samples collected from ancient skeletons, the researchers concluded that lactase persistence did not become common until 1,000 BC, about 4,000 years after it was first discovered.
And they argue that this mutation was important for survival during famines and epidemics, not during times of plenty: undigested lactose could lead to severe intestinal diseases and death.
Using the archaeological record to identify periods of population contraction, they concluded that people were more likely to drink milk when all other food sources were exhausted, and that during those periods, diarrhea was likely to escalate from mild to fatal.
George Davy Smith, an epidemiologist at the University of Bristol who joined the researchers in an analysis of contemporary data on milk and lactase persistence in the current population, said the study raises “fascinating questions” about what some believe lactose is. Intolerant “It would be better if they drank milk.”
A quarter of Americans are lactose intolerant. In A case was filed last yearA panel of U.S. doctors has asked why the USDA’s dietary guidelines recommend so much dairy — suggesting the federal agency cares more about the interests of the meat and dairy industries than the health of Americans.
Previous studies have suggested that people need to rely heavily on milk before individuals can tolerate it in abundance. A small study in 2014 The variant that allows humans to digest lactose did not appear in Hungarian DNA samples until 3,000 years ago, whereas it may have developed as early as 7,000 years in places like Ireland where cheesemaking was prevalent.
Amber Milan, an expert on milk tolerance at the University of Auckland, said the idea that the lactase mutation was important for survival when Europeans began to endure epidemics and famines was a “sound theory” and “supported by previous research on genetic selection drivers”. .”
However, he added that he was not sure the new study “absolutely rules out widespread milk consumption as the evolutionary force behind lactose intolerance” – because the genetic data was collected from Biobank, a British biomedical database of genetic and health information. About 500,000 people.
The authors also focused on a major European genetic variant for lactase persistence — which, while relevant to this study, “might miss other genetic variants that result in lactase persistence,” Milan said.