The world’s oldest cheese was discovered on a 3,600-year-old mummy in China

The white substance, found on the head and neck of a mummy at the Xiaohe cemetery in the Tarim basin, was initially discovered about two decades ago. Although identified as an organic compound, it was not until recently that advanced DNA analysis revealed that the substance is actually an ancient type of kefir cheese. The research results are published in the journal Cell on September 25, confirmed that this is the oldest sample of cheese ever found.

Kefir cheese, a soft and healthy cheese, is produced through the fermentation of milk with kefir grains – a symbiotic mixture of bacteria and yeast. These complex microbial cultures are responsible for converting milk into cheese, similar to how sourdough ferments bread. Further analysis determined that this ancient cheese sample contained microorganisms such as Lactobacillus kefiranofaciens and Pichia kudriavzevii bacterial species still exist in modern kefir grains.

The preservation of cheese over thousands of years is extremely rare in archaeology, which makes this discovery especially valuable in better understanding the diets and cultural practices of ancient peoples. The team of scientists used advanced technical methods, including DNA collection and short sequencing, to extract and analyze DNA samples from the cheese. Qiaomei Fu, a paleontologist at the Chinese Academy of Sciences, said that the study of this ancient cheese provides a unique perspective on the diet and culture of the Bronze Age Xiaohe people.

One of the intriguing findings from the study was the presence of cow and goat DNA in the cheese samples. This suggests that Xiaohe residents used milk from many ruminant species to produce cheese. In particular, milk from cows and goats seems to be used separately, not mixed like some modern cheese making methods.

Producing cheese through fermentation may have been a practical solution for the people of Xiaohe, especially given that many people at that time were lactose intolerant. Fermentation reduces the amount of lactose in milk, allowing people with lactose intolerance to consume dairy products without digestive problems. In addition, fermentation also helps prolong milk preservation, which is very important in a harsh environment like the Tarim basin, where the climate is arid and resources are scarce.

By examining the mitochondrial DNA of goats used to make cheese, researchers discovered that there was a close connection between the Xiaohe population and other ancient populations in Europe and Central Asia. DNA from goats at this site clustered with samples from the European Neolithic and Bronze Age Chalcolithic, suggesting cultural interaction and migration between the steppe and Xiaohe communities.

In addition to providing information about ancient diets, this study also revealed interesting information about the microbial communities that existed in ancient kefir cheese. Surprisingly, some of these ancient cheese samples still retain their original microbiological structure, with little contamination from outside bacteria despite being in existence for thousands of years. This suggests that kefir cheese may have been able to protect itself from contamination, an important factor in the cheese’s survival in a time when microorganisms were not well understood.

One of the most important achievements of this research is the reconstruction of the genome of Lactobacillus kefiranofaciens ancient. By comparing this ancient genome with modern strains, the researchers were able to trace the spread of kefir production techniques across Eurasia. Analysis suggests there are two distinct routes of spread for the subspecies L. kefiranofaciens . One route may have traveled from the North Caucasus to Europe and East Asia, while the other from Xinjiang to the East Asian hinterland such as Tibet and the Gan-Qing region.

This discovery not only helps us better understand cultural practices among ancient populations, but also illustrates how bacteria have evolved and adapted over time. Researchers found that the genome of L. kefiranofaciens ancient times underwent some changes due to horizontal gene transfer, a process by which bacteria transfer genes from one species to another. These changes help the bacteria better adapt to the human environment, including the ability to resist stress, protect against infection from bacteriophages, and interact with human hosts.

These transferred genes helped the bacteria survive in harsh environments and may have been naturally selected for by ancient humans through animal husbandry and kefir production. This opens up a new avenue of research into how culturally important microorganisms have evolved alongside humans over thousands of years.

One of the unanswered questions is why cheese was smeared on mummies at Xiaohe cemetery. Although the specific reason remains unclear, this suggests that cheese may have had a role in the burial rituals or spiritual beliefs of ancient people. It adds another layer of complexity to our understanding of the customs and beliefs of ancient populations, especially in rituals related to death and burial.