Researchers have discovered 3,600-year-old cheese on mummified bodies in China's Xiaohe Cemetery. DNA analysis confirmed the substance as kefir cheese, made from cow and goat milk. The findings, published in Cell, revealed bacterial and fungal species like Lactobacillus kefiranofaciens, similar to those found in modern kefir grains in the sample. It's world's oldest known cheese, researchers said.