For millennia, the Taklamakan Desert environment preserved more than the bodies of those buried in China’s Tarim Basin. Scattered around the necks of some laid to rest in Xiaohe, a Bronze Age cemetery, archaeologists found pebble-sized hunks of a yellowish substance: the world’s oldest cheese. A new analysis of the ancient dairy’s DNA hints at how it was made and how its production spread, researchers report today in Cell.

In a previous study, researchers took tiny samples of the 3,500-year-old cheese that bedecked the mummies’ necks. An analysis of proteins in those bits revealed the presence of Lactobacillus kefiranofaciens, a microbe used to produce a type of fermented cheese called kefir. That was “really amazing,” says Qiaomei Fu, a paleogeneticist at Chinese Academy of Sciences in Beijing. Having worked with ancient human DNA, she wanted to study the fermenting microbe’s DNA.

But “to extract genomes from these ancient samples is not trivial,” Fu says. The tiny amount of DNA left in the ancient cheese has degraded into tiny fragments over time and mixed with genetic information from the environment. In 2014, Fu began designing special molecules that could efficiently capture the microbe’s ancient DNA from the cheese. After years of work, the team has compiled a genome for the ancient organism that is 92 percent complete.