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Study Reveals Lactose Tolerance Happened Quickly in Europe

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The News in Brief:

  • A new study published in Current Biology reveals that the ability for humans to digest milk (lactase persistence) spread through Central Europe quickly in evolutionary terms.
  • The study tested genetic material from the bones of warriors in Germany in 1,200 BC, and researchers found that lactase persistence spread in only a few thousand years.
  • The finding suggests that being able to digest milk may have conferred a major evolutionary advantage for these ancient European peoples who passed the lactase-persistent gene to future generations.

STONY BROOK, NY, September 3, 2020 – The ability for humans to digest milk as adults has altered our dietary habits and societies for centuries. But when and how that ability – known as lactase persistence or lactose tolerance – occurred and became established is up for debate. By testing the genetic material from the bones of people who died during a Bronze Age battle around 1,200 BC, an international team of scientists including Krishna Veeramah, PhD, of Stony Brook University, suggest that lactase persistence spread throughout Central Europe in only a few thousand years, an extremely fast transformation compared to most evolutionary changes seen in humans. Their findings are published in Current Biology.

Despite the prominence of milk drinking in Europe and North American today, approximately two-thirds of the world’s population remains lactose intolerant. Generally, no mammal digests milk as an adult, which is why for example people should not give adult cat or dog pets milk. However, a subset of humans have a genetic mutation that enables the enzyme lactase to digest the lactose sugar found in milk throughout an individual’s lifetime. Many of these people are from Central or Northern Europe.

Bonesatbattlefieldsite 1
Various bones at a Bronze Age battle excavation site, some of which were genetically tested to determine the presence of the lactase-persistent gene. Credit: Stefan Sauer / Tollense Valley Project

The battle occurred on the banks of the Tollense, a river in present day Germany. It is the most significant battle that is known about Bronze Age Europe, probably consisting of about 4,000 warriors, almost a quarter of which died during the fighting. Despite being more than three thousand years old, the researchers were able to sequence DNA from some of the bone fragments recovered from the battle site.

Veeramah, Associate Professor in the Department of Ecology and Evolution in the College of Arts and Sciences, led part of the research that involved analyzing how the overall genetic ancestry of the battlefield population compared to other modern and ancient populations. He and colleagues then compared the frequency of the lactase-persistent allele to other modern and ancient populations, particularly medieval European populations.

The research team, led by Joachim Burger and colleagues at Johannes Gutenberg University Mainz (JGU), found that despite the battle occurring more than 4,000 years after the introduction of agriculture in Europe – which in part would have involved the consumption of dairy from early cattle, goats and sheep domesticates – only one in eight of the warriors had a genetic variant that enabled them to break down lactose.

“When we look at other European genetic data from the early Medieval period less than 2,000 years later, we find that more than 60 percent of individuals had the ability to drink milk as adults, close to what we observe in modern Central European countries, which ranges from 70 to 90 percent” said Veeramah. “This is actually an incredibly fast rate of change for the gene that controls milk digestion. It appears that by simply possessing this one genetic change, past European individuals with the ability to digest lactose had a six percent greater chance of producing children than those who could not. This is the strongest evidence we have for positive natural selection in humans.”

Burger, lead author, added that there still is not definitive answer to the question: Why did being able to digest the sugar in milk after infancy provide such a big evolutionary advantage?

“With milk being a high-energy, relatively uncontaminated drink, its ingestion may have provided greater chances of survival during food shortages or when supplies of drinking water may have been contaminated,” explained Burger.

About Stony Brook University:

Stony Brook University, widely regarded as a SUNY flagship, is going far beyond the expectations of today’s public universities. With more than 26,000 students, 2,700 faculty members, over 200,000 alumni, an academic medical center and 18 NCAA Division I athletic programs, it is one of only four University Center campuses in the State University of New York (SUNY) system. The University embraces its mission to provide comprehensive undergraduate, graduate, and professional education of the highest quality, and has been ranked among the top 35 public universities in the nation by U.S. News & World Report. Fostering a commitment to academic research and intellectual endeavors, Stony Brook’s membership in the Association of American Universities (AAU) places it among the top 65 research institutions in North America. The University’s distinguished faculty have earned esteemed awards such as the Nobel Prize, Pulitzer Prize, Indianapolis Prize for animal conservation, Abel Prize and the inaugural Breakthrough Prize in Mathematics. Part of the management team of Brookhaven National Laboratory of the U.S. Department of Energy, Stony Brook is one of only eight universities that has a role in running a national laboratory. Providing economic growth for neighboring communities and the wider geographic region, the University totals an impressive $7.23 billion in increased economic output on Long Island. Follow us on Facebook (https://www.facebook.com/stonybrooku/) and Twitter (@stonybrooku).

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