Ancient Mongolian Teeth Demand New Research Into the Mysterious Origins of Lactose Intolerance in Humans
Over 3000 years ago, the Steppes of Mongolia were dominated by herds of horses, sheep, cows and yaks, and the humans that ate them, according to a new study published this week in the Proceedings of the National Academy of Sciences (PNAS), “milked their animals as well.” However, it is known that the same people were lactose intolerant, causing a temporary historical paradox. Could this study help explain the origins of lactose intolerance in humans?
‘Lactose intolerance’ is a term used to describe a very common digestive problem (curse) that affects over 75% of humans on the planet. It is diagnosed when the body is unable to digest lactose, the primary carbohydrate (sugar) in milk and dairy products and its digestion by sufferers causes symptoms including; bloated stomach, cramps, pains, feeling bloated, flatulence (wind), and sometimes diarrhea.
Cattle in Mongolia. (CC0)
Early Mongolians were Lactose Intolerant but still Milked their Animals
What has been called “a ground breaking” new study was discussed in an article in ScienceMag which describes it as “cutting-edge analysis of deposits on ancient teeth”, revealing that early Mongolians milked their animals as well. And while this might not sound particularly startling news, “DNA analysis of the same ancient individuals shows that as adults they lacked the ability to digest lactose.”
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What we have here is a case of lactose intolerant ancient adults drinking milk, and apparently getting away with it. “So what’s going?” We might rightfully ask.
Christina Warinner of the Max Planck Institute for the Science of Human History (MPI-SHH) in Jena, Germany, said in the PNAS paper “The findings present a puzzle, challenging an oft-told tale of how lactose tolerance evolved.” “We know now dairying was practiced 4000 years before we see lactase persistence [the ability to digest lactase].” “Mongolia shows us how,” added Warinner.
Map of the Eurasian steppes. ( A) Distribution of the Western (brown) and Eastern (green) steppes and the locations of ancient (red) and modern (black) populations discussed in study. A box indicates the location of the LBA burial mounds surveyed in the Arbulag soum of Khövsgöl aimag. ( B) Enhanced view of LBA burial mounds (white circles) and burial clusters selected for excavation (boxes a–f) with the number of analyzed individuals in parentheses. ( C) Photograph of burial 2009-52 containing the remains of ARS026, a genetic outlier with Western steppe ancestry. (Choongwon Jeong et al., 2018)
It has traditionally been the belief of anthropologists and archaeologists that most people lose the ability to digest lactose in adulthood. In ancient pastoralist cultures, DNA mutations allowed many adults to digest milk, a state known as ‘lactase persistence.’ But a closer look at the teeth of ancient Mongolians reveals that even though "more than a third of their calories” came from cheeses, yogurts, and other fermented milk products, “95% of those people are lactose intolerant” stated the new research paper.
Warinner and her team analyzed human remains from six sites in northern Mongolia that belonged to the Deer Stone-Khirigsuur Complex, a culture that existed between 1300 and 900 BC. MPI-SHH researcher Shevan Wilkin took dental calculus samples from nine skeletons to test for animal proteins. The results showed the people ate dairy products made from “sheep, goats, and bovines such as yak or cow, yet they were lactose intolerant.”
Bacteria’s Role in the Origins of Lactose Intolerance
Warinner says “Modern Mongolians digest dairy by using bacteria to digest lactose for them, turning milk into yogurt and cheese, along with a rich suite of dairy products unknown in the Western diet.” She suspects that the ancient Mongolian pastoralists must also have adopted similar strategies for the “Control and manipulation of microbes” which she says, “is core to this whole transformation.”
Mongolian dairy products - Aaruul, Eezgii. (Takeshi KITAYAMA/CC BY NC SA 2.0)
If the speculations of Warinner and her team are right, all the thousands of geneticists who believed lactase persistence and dairying were linked, must now accept they were quite simply wrong, and rethink why the adaptation is common within some dairying populations yet untraceable in others.
An even more fundamental question will hopefully be answered by Warinner’s team in the near future: how did dairying even reach Mongolia so early in the first place? In the Bronze Age, the Yamnaya’s genetic signature replaced many Asian and European populations, but they abruptly stopped west of Mongolia at the Altai Mountains. “Culturally, it’s a really dynamic period,” Warinner says and she thinks that even though the Yamnaya “didn’t contribute their genes to East Asia, they did spread their culture, including dairying.”
The new study’s perplexing results will soon begin phase two, which aims to gain a better understanding of “how Mongolians and other traditional dairying cultures harnessed microbes to digest milk and render lactose tolerance irrelevant and to figure out which of hundreds of kinds of bacteria make the difference.”
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A herder woman milks her yaks in Must, Khovd Province, Mongolia. (United Nations Photo/CC BY NC ND 2.0)
When Did Humans Start Dairying?
To date, the earliest archaeological evidence for ‘dairying’ (the processing of milk fats) is around the seventh millennium BC in northwestern Anatolia, the sixth millennium BC in eastern Europe, the fifth millennium BC in Africa, and the fourth millennium BC in Britain and Northern Europe. However, a research article published on ThoughtCo informs that goats were first domesticated in western Asia about 11,000 years ago and in the eastern Sahara cattle were being farmed no later than 9,000 years ago.
Archaeologists have always surmised that the primary reason for this was for an easier source of meat than hunting, but this new study opens history right up again and it must now be considered that maybe some of these pre-historic people milked their animals and made cheeses, gloopy creams, and yogurts. If so, ‘Ancient Greek’ yogurt might soon have to be rebranded Ancient Anatolian, or African, yogurt.
Greek yogurt with strawberries and honey. (Janine/CC BY 2.0)
Top Image: ‘Waiting yak.’ A new study analyzing ancient Mongolian teeth may help explain the origins of lactose intolerance in humans. Source: Fotolia
By Ashley Cowie