You are most likely lactose intolerant. You’re not alone — 5,000 years ago, most humans were also lactose intolerant.
A new study published Wednesday in the journal Nature by researchers from the University of Bristol and University College London found that the ability to digest lactose became common some 5,000 years after the first signs of breast milk consumption, which date back to around 6,000 BC. I discovered that
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They also used new computer modeling techniques to find that milk consumption was not the reason for the increased lactose tolerance.
“Milk didn’t help at all,” study author Mark Thomas, a researcher at University College London, told DW.
“I’m excited about the statistical modeling method we’ve developed. To my knowledge, no one has done it,” Thomas said.
What is lactose intolerance?
All babies can normally digest lactose. However, in most cases, this ability begins to wane when breastfeeding is stopped.
Today, about two-thirds of people are lactase-nonpersistent and cannot digest lactose, the main sugar in milk.
Lactase nonpersistent people are unable to produce an enzyme called lactase that breaks down lactose. In the absence of this enzyme, lactose moves freely into the colon, where bacteria eat it.
This can lead to unpleasant side effects such as cramping, gasping and diarrhea. Collectively these symptoms are called lactose intolerance.
The results of the study run counter to the widely held belief that dairy consumption by our prehistoric ancestors evolved genetic mutations that allowed us to digest lactose into adulthood.
This assumption can be traced, in part, to marketing claims of the health benefits of lactose tolerance. We have marketed milk and dairy products as an important supplement and a good source of uncontaminated water.
But researchers quickly dismissed those ideas after analyzing vast amounts of DNA and medical information from people in the UK. Lactose tolerance has been found to have little effect on a person’s health, calcium levels, or whether they drink milk.
Why did lactase persistence evolve?
Genetic studies have shown that lactase persistence is “the most strongly selected single genetic trait to have evolved in the last 10,000 years.”
Around 1,000 BC, the number of humans with the ability to digest lactose, encoded in one gene, began to grow rapidly.
After finding that milk consumption was not behind this surge, researchers tested two alternative hypotheses.
One hypothesis was that as humans become exposed to more pathogens, the symptoms of lactose intolerance could combine with new infectious agents and become fatal.
“We know that exposure to pathogens has increased over the past 10,000 years as population density has increased as people have lived closer to livestock,” Thomas said.
Another hypothesis concerned famine. When crops sown by lactose-intolerant prehistoric populations failed, milk and dairy products became some of the only nutritional options.
“A healthy person would have diarrhea.
The researchers used the same computer modeling techniques to investigate whether these ideas could better explain the evolution of lactase persistence.
“And they were much better,” Thomas said. “Ultimately all these theories related to milk use seem to be useless.”
This study focused primarily on European populations, and more research is needed on other continents.
Unfortunately, finding ancient DNA in African countries is more difficult. because it’s hotter.
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