The Mongol Empire reached the height of its power in the 13th century. It was also during this time that yak milk became a popular drink among its elite, a new study has found.
By analyzing proteins found within ancient dental calculus, an international team of researchers provides direct evidence for the consumption of milk from yaks. In addition, they discovered milk and blood proteins associated with both horses and other animals. The team’s results are published in Communication Biology.
The study presents novel protein findings from an elite Mongol Era cemetery with exceptional preservation in the permafrost. This is the first example of yak milk recovered from an archaeological context.
Yaks are large herbivores that can weigh up to 1,000 kilograms. They were originally domesticated in Tibet, but the use of the animal spread northwards. The study explains that yaks were very useful in the regions of the medieval Mongol Empire:
The domesticated yak is well adapted to cold and high-altitude alpine tundra ecosystems. Yaks are able to survive temperatures lower than −40 °C, as well as obtain water by eating snow and ice, while accessing covered winter forage, including grasses, shrubs, moss, and lichens, by digging under snow. For communities living at high altitudes in eastern Eurasia, yak products provide an important source of calories, as well as commodities for local consumption and exchange. Yak milk is high in fat, making it ideal for producing butter and cheese, and for the manufacture of candles and lamps. The hair from yaks can be made into textiles and felts while the animal’s dried dung functions as an important fuel source for heating and cooking, making it a critical resource in regions where wood is scarce. Yaks are regularly used for traction and transport, connecting human communities at high altitudes.
Previous research indicates that milk has been a critical resource in Mongolia for more than 5,000 years. While the consumption of cattle, sheep, goat and even horse milk have securely been dated, until now, when people began drinking milk from yaks has been difficult to determine. Understanding when and where humans domesticated this iconic species has been limited to rarely recovered yak remains and artistic depictions of yaks. However, whether these are wild or domestic is unclear.
The discovery of an elite Mongol-era cemetery in northern Mongolia was surprising to the researchers. “Our most important finding was an elite woman buried with a birchbark hat called a bogtog and silk robes depicting a golden five-clawed dragon. Our proteomic analyses concluded that she drank yak milk during her lifetime,” said Alicia Ventresca-Miller, an Assistant Professor of Anthropology at the University of Michigan who co-led the study. “This helped us verify the long-term use of this iconic animal in the region and its ties to elite rulers.”
Located along a high-elevation ridgeline covered in mist, the location bears the name ‘Khorig,’ meaning taboo. It may be that this cemetery was considered elite, as the researchers recovered evidence of connections to the ruling elite, including a five-clawed dragon depicted on a Cizhou vessel and a traditional robe, or deel.
“Ceramic vessels were turned into lanterns made of dairy products, which revealed long-standing religious ideas and the daily life of the elites of the Mongol empire,” said Jamsranjav Bayarsaikhan, a researcher at the Max Planck Institute for the Science of Human History and the National Museum of Mongolia.
Archaeologists have spent years collecting and conserving pieces of silk and leather strewn across the surface near the burials. Unfortunately, over the past few decades the permafrost has begun to melt and the sites have been heavily looted. “The degree of looting that we are seeing is unprecedented,” notes Julia Clark of Nomad Science. “Nearly every burial that we can locate on the surface has recently been destroyed by looting activity.”
Archaeologists have long suspected that this area was important, and it remains one of the primary areas of yak herding in the present day. While much was lost to looters, what remained of the burials was still well preserved within the permafrost. This allowed the researchers to use proteomic analysis of dental calculus to identify the diets of Mongol-era elites. They found proteins associated with milk, blood and other tissues that had been consumed by different individuals.
“What is really exciting is that between cows and yaks, there is only a single difference in the amino acid sequence in the most commonly recovered milk protein, and in this case, we were able to recover the part which is specific to yak, Bos mutus,” said study co-lead Shevan Wilkin of the University of Zurich and Max Planck Institute for the Science of Human History.
Due to the incredible preservation made possible through the permafrost environmental conditions, the team was able to identify intriguing proteins recovered for the first time from archaeological samples. These included horse milk curd proteins as well as caprine and equine blood proteins that had not been previously recovered from dental calculus.
The study, “Permafrost preservation reveals proteomic evidence for yak milk consumption in the 13th century,” by Alicia R. Ventresca Miller, Shevan Wilkin, Jamsranjav Bayarsaikhan, Abigail Ramsøe, Julia Clark, Batsuren Byambadorj, Sandra Vanderwarf, Nils Vanwezer, Ashleigh Haruda, Ricardo Fernandes, Bryan Miller and Nicole Boivin, appears in Communications Biology. Click here to read it.