"the 10,000 years since the advent of agriculture is a very small evolutionary time step"
True, although those 10,000 (I've actually heard 20-40K) years are the most recent ones in our evolution and therefore have more direct bearing on our current state. In addition, humans experienced a population bottleneck around 60,000 that brought us down to 10-20K individuals. Since then, there have been repeated agricultural famines. These stresses should have favored people able to eat the grains that formed the basis of our diet.
True, although those 10,000 (I've actually heard 20-40K) years are the most recent ones in our evolution and therefore have more direct bearing on our current state. In addition, humans experienced a population bottleneck around 60,000 that brought us down to 10-20K individuals. Since then, there have been repeated agricultural famines. These stresses should have favored people able to eat the grains that formed the basis of our diet.