CAMBRIDGE, MASSACHUSETTS—Waterproof, heatproof containers were made at least 10,000 years ago, according to Ofer Bar-Yosef of Harvard University. He and his team found such pots in a cave in China. “When you look at the pots, you can see that they were in a fire,” he explained. The pots may have been used for boiling soup or alcohol. And 25,000 years ago, soup may have been made by dropping heated rocks into a lined pit with water and other ingredients. Such broths would have balanced the diet and may even have been cooked by Neanderthals, since cooked starched grains have been found on their 46,000-year-old teeth. “This doesn’t prove that they were making soups or stews, but I would say it’s quite likely,” said John Speth, an emeritus professor of anthropology at the University of Michigan.