Quote from the Paleo diet website- Right On!!

Our genome was conditioned and shaped by environmental selective pressures that occurred long before the Agricultural Revolution. Since the appearance of our genus Homo, more than 2 million years ago, there have been at least 100,000 generations. Since the Agricultural Revolution of 10,000 years ago there have been only 500 human generations. Our genome simply has had insufficient time to adapt to the foods ushered in during the Neolithic (fatty meats, dairy products, whole grains and salty foods).