They also say that 10,000 years may have been enough time for people to adapt to diets with food grown through farming. For example, alleles that helped people eat dairy became common in Europe just a few thousand years after people started raising animals. There is also evidence that the diet of Stone Age humans may have had some form the refined starches and grains that are not part of the paleolithic diet. A 2010 study showed the discovery of a 30,000 year old mortar and pestle from which flour of several plants were isolated.