Study reveals lactose tolerance happened quickly in Europe

Date:
September 3, 2020
Source:
Stony Brook University
Summary:
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.



FULL STORY ==========================================================================
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.

The battle occurred on the banks of the Tollense, a river in present day Germany, and is the most significant that we know about from 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, and 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." Joachim Burger of JGU, lead author on the
study, 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.


========================================================================== Story Source: Materials provided by Stony_Brook_University. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Joachim Burger, Vivian Link, Jens Blo"cher, Anna Schulz, Christian
Sell,
Zoe' Pochon, Yoan Diekmann, Aleksandra Žegarac, Zuzana
Hofmanova', Laura Winkelbach, Carlos S. Reyna-Blanco, Vanessa
Bieker, Jo"rg Orschiedt, Ute Brinker, Amelie Scheu, Christoph
Leuenberger, Thomas S.

Bertino, Ruth Bollongino, Gundula Lidke, Sofija Stefanović,
Detlef Jantzen, Elke Kaiser, Thomas Terberger, Mark G. Thomas,
Krishna R.

Veeramah, Daniel Wegmann. Low Prevalence of Lactase Persistence
in Bronze Age Europe Indicates Ongoing Strong Selection over the
Last 3,000 Years.

Current Biology, 2020; DOI: 10.1016/j.cub.2020.08.033 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200903114212.htm

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