Humanity's shift from foraging to agriculture necessitated dramatic changes in nutritional patterns which had existed since the origin of our genus over two million years earlier. In the industrial era, our diet has departed still further from its original pattern. These cultural innovations have far outstripped the capacity of genetic evolution to keep pace so a gap has been created between our intrinsic genetic makeup and current eating habits. This phenomenon has important implications for human health. Increased consumption of saturated fat affects serum cholesterol levels and coronary heart disease. Unbalanced intake of w-6 and w-3 highly unsaturated fatty acids influences blood coagulability, atherogenesis, and possibly psychiatric depression. High glycemic index carbohydrates. exacerbate insulin resistance and diabetes mellitus. Excessive sodium and deficient potassium lay the foundation for essential hypertension. And cereal grains, rarely consumed by free-living, nonhuman primates, now comprise 50% (or more) of human energy intake. They thereby replace a corresponding proportion of the foods which fueled human evolutionary development. Phytochemicals integral to fruits and vegetables and associated, epidemiologically, with lower cancer risk have been partially replaced by cereal grain phytochemicals which appear less, if at all, effective cancer preventive agents. To an astonishing extent, dietary risk factors for chronic degenerative diseases, established by epidemiological, mechanistic, and clinical investigations, recapitulate differences between preagricultural and current nutritional experience. That preventive recommendations increasingly resemble paleoanthropological reconstructions of the ancestraL human diet testifies to its continuing relevance.