To live by exploiting grain crops, humans must process the grain before it can be eaten. Human teeth, jaws, and digestive tract are simply not adapted for this kind of diet. The typically human solution to this problem is, however, not to evolve biologically, but to find cultural or technical solutions to problems: in this case, to develop the knowledge and techniques for processing grain.
One early and universal technique of transforming grain into food is to mill the seeds slightly between two stones and then to boil the grain in water, making a kind of gruel. If ground into coarse meal, boiling in water will produce something like the oatmeal we still eat at breakfast. If ground fine and mixed with water into a paste and then baked, the grain is transformed into bread. The yeast cultures which leaven some forms of bread are naturally occuring, but were regarded as magical prior to the relatively recent discovery of micro-organisms.
If stored grain gets wet and begins to sprout, the stored carbohydrates in the seed begin converting into sugar. While the grain is spoiled for bread-making, it can still be consumed if treated in another process called fermentation. The sprouted grain is first baked, ground into a paste (called malt), and then added to water. With the right yeast and little luck, the result is beer, another of the food inventions of early agriculturalists.
To live by exploiting grain crops, humans must process the grain before it can be eaten. Human teeth, jaws, and digestive tract are simply not adapted for this kind of diet. The typically human solution to this problem is, however, not to evolve biologically, but to find cultural or technical solutions to problems: in this case, to develop the knowledge and techniques for processing grain.