There seems little doubt among anthropologists that we humans cut our evolutionary teeth on a diet largely composed of meat and fat for the vast majority of our existence. Carbohydrates simply were not available much of the year -- even in equatorial Africa there are definite fruiting and non-fruiting seasons. And during long stretches of ice age conditions our ancestors would simply have died out if they had been dependent on plant foods for any substantial part of their diet. Luckily we came from a long (very long) line of expert hunters. In terms of human evolution, agriculture and the cultivation of grains, etc. is the 'new kid' on the block. -- the real 'fad' diet.
Anthropologists further inform us that paleolithic man was in many way healthier than his neolithic progeny. Generally, in most parts of the world, whenever cereal-based diets were first adopted as a staple food replacing the primarily animal-based diets of hunter-gatherers, there was a characteristic reduction in stature, a reduction in life span, an increase in infant mortality, an increased incidence of infectious disease, an increase in diseases of nutritional deficiencies (i.e., iron deficiency, pellagra), and an increase in the number of dental caries and enamel defects. Only in the 20th century, with increased protein consumption, have we begun to attain our true stature.
Since 99.99% of our genes were formed before the development of agriculture, from a biological perspective, we are still hunter-gathers.Thus, our diet should reflect the sensibilities of this nutritional niche: meats, including organ meats; eggs; fish and seafood; good quality natural fats (cold-pressed olive oil or coconut oil); low glycemic vegetables (more colorful the better) and fruit, such as berries and melons (modern agriculture has significantly increased the sugar and starch content of vegetables and fruits over their Paleolithic counterparts), nuts and seeds - the evolutionary diet. Most dairy is ok since it is animal protein and fat. However, consume grains and legumes sparingly.
Keep all refined, processed food to a minimum -especially those made with white flour, sugar, hydrogenated fats and artificial flavorings! Remember to your stone age body, these 'food products' are alien, as in, not from this planet. They create abnormal surges in blood sugar which in turn calls up insulin. Insulin is a valuable hormone which, among other things, packs away excess carbohydrates (that in nature only occur in quantity in summer) into fat stores. This fat saw our ancestors through many a cold winter. However, in our modern life, we have access to carbohydrates 24/7, year in and year out. We never get a chance to burn down the fat pad. Many of today's chronic diseases, including heart disease, obesity, diabetes and cancer are thought by many researchers to be caused by chronic hyperinsulinemia and insulin resistance. Consume foods as close to their natural, whole state as possible.