The Paleolithic people subsisted on whole foods, fruits, vegetables, nuts, fish, and wild game.
Scientists are finding that a deviation from a diet similar to our ancestors, the Paleoliths, has serious health implications that can lead to chronic diseases like diabetes, heart disease, and cancer. This is because our genome has changed little since the beginnings of agriculture, so genetically we are adapted for Stone Age cuisine.
Although the Paleolithic diet included meat as 65% of their energy source and 35% from gathered plant food, they were free of heart disease. Scientists think this is because of the beneficial ratios of monounsaturated fats, polyunsaturated fats, omega-6 to omega-3, and other lifestyle characteristics that differ from the Western or American diet.
Cordain L, Eaton SB, Miller JB, Mann N, Hill K. The paradoxical nature of hunter-gatherer diets: meat-based, yet non-atherogenic. Eur J Clin Nutr 2002