Scientists Discovered The World’s Oldest Cheese—Smeared On Mummies

Found spread on the heads and necks of several mummies in the Xiaohe cemetery in Northwest China’s Tarim Basin two decades ago, scientists at the time believed the substance to be a fermented dairy product. But they had no way of finding out more, and the discovery—which dated back to the Bronze Age—remained a complete mystery. Fu’s team unraveled it all.

By extracting mitochondrial DNA from the samples found in three different tombs, researchers identified both cow and goat DNA in the cheese. This showed that the Xiaohe people used differing types of animal milk in separate batches, in contrast to the mixing of milk types common in Middle Eastern and Greek cheesemaking.

Fu and her colleagues recovered the DNA of microorganisms from the dairy samples and confirmed it to be kefir cheese, thanks to the bacterial and fungal species Lactobacillus kefiranofaciens and Pichia kudriavzevii, respectively. Both species are common in present-day kefir grains. These grains are symbiotic cultures containing multiple species of probiotic bacteria and yeast, which ferment milk into kefir cheese much like how a sourdough starter works.

Sequencing the bacterial genes in the ancient kefir cheese allowed the team to track how probiotic bacteria evolved over 3,500 years. Today, two major groups of the Lactobacillus bacteria are frequently used in yogurt- and cheese-making, one of which originates in Russia and the other in Tibet. The Russian type is dominant globally—including in the United States, Japan, and European countries—but the team found that the samples from the ancient Chinese tomb more closely relate to the Tibetan group, challenging a long-held belief that kefir originated solely in the mountainous North Caucasus region of modern-day Russia.

“Our observation suggests kefir culture has been maintained in Northwestern China’s Xinjiang region since the Bronze Age,” Fu said in the statement.

The study also explored how the bacteria exchanged genetic material with related strains, improving its genetic stability and milk fermentation capabilities over time. Compared with ancient Lactobacillus, modern-day bacteria are less likely to trigger an immune response in the human intestine, showing that genetic exchanges helped it become more adapted to human hosts over thousands of years.

“This is an unprecedented study,” Fu said, “allowing us to observe how a bacterium evolved over the past 3,000 years. Moreover, by examining dairy products, we’ve gained a clearer picture of ancient human life and their interactions with the world. This is just the beginning, and with this technology, we hope to explore other previously unknown artifacts.”