Not to mention the fact (already mentioned) that anthropologists have documented a few different bad things that happened to humans when we switched from a hunter/gatherer diet to an agricultural diet using grains as staples: shorter life expectancy, smaller stature, and weaker.
Ask a veterinarian whether dogs are better off eating food loaded with grains or without it. The answer is without, and the reason is "because they didn't evolve eating grains."
