It now seems that humans began to grind grain into flour earlier than was originally thought. Grinding stones have been found at African and Asian sites dating from 200,000-50,000 years ago. It was presumed at first that these stones were used primarily to grind plant and animal materials. or minerals to make pigments. rather than for the preparation of foodstuffs. However, new findings from the Middle East raise the intriguing possibility that some human groups may have been using grinding stones to process cereal grains, such as wheat, and maybe other types of edible plant, as early as the Middle Paleolithic Era （i.e. 50,000 years ago and earlier）。 But why is it such an advantage to grind cereal grains before eating them？ The main reason is that grinding breaks down the hard, fibrous cereal grain to release the easily digestible starch granules contained within. This served two purposes. Firstly, it enabled people to save enormously on the wear and tear of their teeth. compared to eating raw, unprocessed grains. Unlike the teeth of grazing animals, human teeth do not continue to grow after childhood. Tooth wear due to a diet high in fiber and raw plants can result in the substantial erosion of molars （back teeth） by early adulthood. People with worn or absent teeth faced starvation unless they could find alternative types of food that did not require chewing. Alternatively, they could try to find another way of grinding the fibrous plant material before eating it. Perhaps it was one of these incentives that led to the use of stone grinding tools for seed processing.

The development of grinding technology would have been socially advantageous to a human group People would tend to keep their teeth for much longer, and thus older, more experienced individuals could have lived longer, despite the ultimate loss of their teeth. Such people could then serve their clan either as "grandparent" childcare givers or by acting as instruments for the innovation and transmission of oral culture. The latter role was a key adaptation in preliterate societies （societies without writing system）， particularly in relation to strategies for food acquisition and techno log in an era of considerable climatic flux. The remember knowledge of how their grandparents dealt with the last arid period, including alternative food acquisition strategies, would have enabled such surviving elders to greatly enhance the ability of their to deal with such difficult situations.

Unfortunately, grinding seed to make flour could be a mixed blessing. Depending on the type of stone used, the prolonged and laborious process of grinding cereal grains would produce small chips of stone that could get into the flour. People eating the products of such flour every day would be repeatedly exposed to stone chips as they chewed their food, and eventually their teeth might become chipped and worn. This problem was partially alleviated many millennia later by the invention of pottery, which enabled a porridge to be made from grains mixed with water and boiled without grinding.

The second, and more immediate. reason for grinding cereal grains is that it enables us to produce a more attractive, sweeter tasting, more nutritious, and calorie-rich foodstuff. Rather than a hard, dry, indigestible, tooth-destroying cereal grain, people could enjoy foods such as seed cakes. biscuits. and all the various forms of bread that we still relish so much today Cereal grains that have been ground and processed into flour can be much more easily digested due to the higher surface area that is available for digestive enzymes（molecules that break down food）. This means that not only the plentiful starches but also the grain proteins and the much less abundant micronutrients, are more easily absorbed from processed cereals. In the cold, dry climate of the Last Glacial Maximum, plants of the grass family such as cereals would have been more reliable source of food than woodland plants（e.g. nuts and berries）。 Many of these woodland plants would have died out as the weather worsened. and edible animals would have also become increasingly unavailable as they migrated to warmer climates, leaving cereals as one of the few remaining options for the people who chose, or were obliged, to remain in the Middle East.