Dairy foods helped ancient Tibetans thrive in one of Earth's most inhospitable environments

Now, a new study in the journal Science Advances reveals that dairy was a key component of early human diets on the Tibetan Plateau. The study reports ancient proteins from the dental calculus of 40 human individuals from 15 sites across the interior plateau.

"We tried to include all the excavated individuals with sufficient calculus preservation from the study region," states Li Tang, lead author of the study. "Our protein evidence shows that dairying was introduced onto the hinterland plateau by at least 3500 years ago," states Prof. Hongliang Lu, corresponding author of this study.

Ancient protein evidence indicates that dairy products were consumed by diverse populations, including females and males, adults and children, as well as individuals from both elite and non-elite burial contexts. Additionally, prehistoric Tibetan highlanders made use of the dairy products of goats, sheep, and possibly cattle and yak. Early pastoralists in western Tibet seem to have had a preference for goat milk.

"The adoption of dairy pastoralism helped to revolutionize people's ability to occupy much of the plateau, particularly the vast areas too extreme for crop cultivation," says Prof. Nicole Boivin, senior author of the study.

Tracing dairying in the deep past has long been a challenge for researchers. Traditionally, archaeologists analyzed the remains of animals and the interiors of food containers for evidence of dairying, however the ability of these sources to provide direct evidence of milk consumption is often limited.

"Palaeoproteomics is a new and powerful tool that allowed us to investigate Tibetan diets in unprecedented detail," says coauthor Dr. Shevan Wilkin. "The analysis of proteins in ancient human dental calculus not only offers direct evidence of dietary intake, but also allows us to identify which species the milk came from."

"We were excited to observe an incredibly clear pattern," says Li Tang. "All our milk peptides came from ancient individuals in the western and northern steppes, where growing crops is extremely difficult. However, we did not detect any milk proteins from the southern-central and south-eastern valleys, where more farmable land is available."

Surprisingly, all the individuals with evidence for milk consumption were recovered from sites higher than 3700 meters above sea level (masl); almost half were above 4000 masl, with the highest at the extreme altitude of 4654 masl.

"It is clear that dairying was crucial in supporting early pastoralist occupation of the highlands," notes Prof. Shargan Wangdue. Li Tang concludes: "Ruminant animals could convert the energy locked in alpine pastures into nutritional milk and meat, and this fueled the expansion of human populations into some of the world's most extreme environments."