Traces of dairy fat in ancient ceramic fragments suggest that people have been making cheese in Europe for up to 7,500 years. In the tough days before refrigerators, early dairy farmers probably devised cheese-making as a way to preserve, and get the best use out of, milk from the cattle that they had begun to herd. Peter Bogucki, an archaeologist at Princeton University in New Jersey, was in the 1980s among the first to suspect that cheese-making might have been afoot in Europe as early as 5,500 bc. He noticed that archaeologists working at ancient cattle-rearing sites in what is...