A mysterious white substance found on the necks of ancient mummies in China turned out to be the world's oldest known cheese. Now, its DNA has given scientists a "clearer picture" of life 3,500 years ago.
Archaeologists first uncovered the Bronze Age dairy product on mummies in the Xiaohe cemetery of northwestern China's Xinjiang province about 20 years ago. Scientists soon identified it as being 3,500 years old and the world's oldest known cheese, according to a news release from Cell Press via Phys.org.
But the most significant breakthrough came only recently when a team of Chinese scientists successfully managed to sequence the DNA of the ancient cheese.
Their work, published Sept. 25 in the peer-reviewed journal Cell, was "unprecedented" and over 11 years in the making, Qiaomei Fu, one of the study's co-authors, said in a news release from the Chinese Academy of Sciences shared via EurekAlert.
So what did they learn about the world's oldest known cheese?
First, researchers confirmed the substance was a kefir cheese, "a fermented milk product made using kefir grains," the institute said. Some samples were made from cow milk and others from ancient Eurasian goat milk, the study said. These ancient goats were genetically "distinct" from the region's modern-day domesticated goats.
Second, researchers identified the genetic origins of the bacteria used in making the ancient cheese. The bacteria was most closely related to strains from Tibet and inland Asia, suggesting it spread separately from the kefir bacteria in Russia and Europe.
Together, these discoveries offered researchers a glimpse into how ancient people made cheese and spread their fermentation practices, the institute said.
"It is exciting to see how much information can be retrieved from these cheeses," Yimin Yang, the study's lead co-author, said in the release. "Organic residues open a window into past human behaviors and culture that were lost in history and records."
Finally, researchers were also able "to observe how a bacterium evolved over the past 3,000 years," Fu said in the release.
The analysis focused on Lactobacillus kefiranofaciens, the main bacteria used in the ancient kefir cheese. By comparing the ancient bacteria with its modern-day counterpart, scientists identified several changes in the DNA makeup such as its "adaptation to environmental stress" and "to the human intestinal environment," the institute said.
"Human-microbial interaction is always fascinating," co-author Yichen Liu said in the release. "Fermentative microbes played such an important role in the daily life of these ancient humans, and they propagated these microbes for thousands of years without knowing the existence of them for most of the time."
"By examining dairy products, we've gained a clearer picture of ancient human life and their interactions with the world," Fu said.
The research employed new techniques to sequence ancient DNA and left scientists optimistic about the potential of future analysis.
"This is just the beginning," Fu said. "With this technology, we hope to explore other previously unknown artifacts."
Researchers did not specify why the mummies were buried with ancient kefir and did not comment on the smell or taste of the cheese.
The research team included Yichen Liu, Bo Miao, Wenying Li, Xingjun Hu, Fan Bai, Yidilisi Abuduresule, Yalin Liu, Zequan Zheng, Wenjun Wang, Zehui Chen, Shilun Zhu, Xiaotian Feng, Peng Cao, Wanjing Ping, Ruowei Yang, Qingyan Dai, Feng Liu, Chan Tian, Yimin Yang and Qiaomei Fu.