Scientists have successfully extracted and analyzed DNA from ancient cheese found near the Tarim Basin mummies in China, which dates back around 3,600 years. The findings indicate a new origin for kefir cheese and provide insights into the development of probiotic bacteria.
In a groundbreaking study, researchers managed to extract and analyze DNA from ancient cheese samples located next to the Tarim Basin mummies, dating to roughly 3,600 years ago. The research, published on September 25 in the journal Cell by Cell Press, indicates a fresh origin for kefir cheese and enhances our understanding of probiotic bacteria’s evolution.
“This is the oldest cheese sample known globally,” states Qiaomei Fu, the lead author from the Institute of Vertebrate Paleontology and Paleoanthropology at the Chinese Academy of Sciences. “Items like cheese are notoriously challenging to preserve over millennia, making this a unique and important find. Detailed analysis of the ancient cheese can reveal much about the diets and cultures of our ancestors.”
About 20 years ago, archaeologists unearthed mysterious white substances on the heads and necks of several mummies in the Xiaohe cemetery in Northwestern China’s Tarim Basin, dating from the Bronze Age, roughly 3,300 to 3,600 years ago. Initially, scientists speculated these substances might be a type of fermented dairy product, yet the exact identification eluded them.
After over a decade of progress in ancient DNA analysis, Fu’s team has solved this puzzle.
They successfully extracted mitochondrial DNA from samples found in three distinct tombs at the site. The team identified DNA from both cows and goats in the cheese. Notably, the ancient Xiaohe people appeared to have utilized different animal milk separately, unlike the common practice of mixing milk types seen in Middle Eastern and Greek cheese production.
Crucially, Fu and her team were able to recover DNA from microorganisms within the dairy samples, confirming that the white substances were indeed kefir cheese. They found bacterial and fungal species such as Lactobacillus kefiranofaciens and Pichia kudriavzevii, which are known to exist in modern kefir grains.
Kefir grains consist of various probiotic bacteria and yeast, which work together to ferment milk into kefir cheese, similar to a sourdough starter.
The ability to sequence the bacterial genes within the ancient kefir cheese provided the researchers with a chance to trace the evolution of probiotic bacteria over the past 3,600 years. They specifically compared the ancient Lactobacillus kefiranofaciens found in the cheese with its modern counterparts.
Currently, there are two main groups of Lactobacillus bacteria – one originating from Russia and the other from Tibet. The Russian variant is the most commonly used in various countries including the US, Japan, and throughout Europe, for making yogurt and cheese.
Interestingly, the study revealed that the Lactobacillus kefiranofaciens found in the ancient samples was more closely related to the Tibetan strain, challenging the long-held belief that kefir culture developed solely in the North Caucasus region of present-day Russia.
“Our findings indicate that kefir culture has been preserved in Northwestern China’s Xinjiang region since the Bronze Age,” Fu adds.
The research also demonstrated how Lactobacillus kefiranofaciens exchanged genetic material with related strains, enhancing its genetic stability and ability to ferment milk over time. In contrast to ancient Lactobacillus strains, modern bacteria are less likely to incite an immune response in the human intestine. This suggests that these genetic exchanges have helped Lactobacillus adapt better to human hosts through centuries of interaction.
“This study is remarkable as it allows us to observe microbial evolution over the past 3,000 years. Furthermore, by examining dairy products, we’ve gained valuable insights into ancient human lifestyles and their connections with the environment,” Fu concludes. “This is just the beginning; we hope to utilize this technology to investigate other unknown artifacts.”
