Mercola with Cordain

"Further, the USDA food pyramid places breads, cereals, rice and pasta at its base and recommends that we consume 6-11 servings of these items daily. Nutritionists at the Harvard School of Public Health (Willett WC. The dietary pyramid: does the foundation need repair? Am J Clin Nutr. 1998;68: 218-219) have recently publicly criticized this recommendation.
It fails to distinguish between refined and complex carbohydrates and their relative glycemic responses. Dr. Willett further pointed out that there was little empirical evidence to support the dominant nutritional message that diets high in complex carbohydrate promote good health.
Both the fossil record and ethnological studies of hunter-gatherers (the closest surrogates we have to stone age humans) indicate that humans rarely if ever ate cereal grains nor did they eat diets high in carbohydrates.
Because cereal grains are virtually indigestible by the human gastrointestinal tract without milling (grinding) and cooking, the appearance of grinding stones in the fossil record generally heralds the inclusion of grains in the diet.
The first appearance of milling stones was in the Middle East roughly 10-15,000 years ago. 
These early milling stones were likely used to grind wild wheat which grew naturally in certain areas of the Middle East. Wheat was first domesticated in the Middle East about 10,000 years ago and slowly spread to Europe by about 5,000 years ago. Rice was domesticated approximately 7,000 years ago in SE Asia, India and China, and maize (corn) was domesticated in Mexico and Central America roughly 7,000 years ago.
Consequently, diets high in carbohydrate derived from cereal grains were not part of the human evolutionary experience until only quite recent times.
Because the human genome has changed relatively little in the past 40,000 years since the appearance of behaviorally modern humans, our nutritional requirements remain almost identical to those requirements which were originally selected for stone age humans living before the advent of agriculture.
Robert Crayhon: What happened to our health when we switched from a hunter-gatherer diet to a grain-based one?
Loren Cordain: The fossil record indicates that early farmers, compared to their hunter-gatherer predecessors had a characteristic reduction in stature, an increase in infant mortality, a reduction in life span, an increased incidence of infectious diseases, an increase in iron deficiency anemia, an increased incidence of osteomalacia, porotic hyperostosis and other bone mineral disorders and an increase in the number of dental caries and enamel defects.
Early agriculture did not bring about increases in health, but rather the opposite. It has only been in the past 100 years or so with the advent of high tech, mechanized farming and animal husbandry that the trend has changed. "


http://www.mercola.com/article/carbohydrates/paleolithic_diet.htm