Up until about 20,000 years ago, all human existed on foods derived almost entirely from hunting and gathering. Over the last 20,000 years, hunting and gathering has largely given way to farming and increasingly varied forms of food processing that has drastically altered the diet of most people worldwide and especially in more developed nations such as the USA. According to S. Boyd Eaton, MD, "we are the heirs of inherited characteristics accrued over millions of years; the vast majority of our biochemistry and physiology are tuned to life conditions that existed before the advent of agriculture some 10,000 years ago. Genetically our bodies are virtually the same as they were at the end of the Paleolithic era some 20,000 years ago (1). Certainly it is true that human beings adapted to their environment in part by evolving their physiology and biochemical "machinery" to meet their nutritional requirements more efficiently. The scientific evidence increasingly shows that many aspects of the typical modern diet and lifestyle do promote the very diseases that increasingly account for a large proportion of the disabilities and deaths seen in modern societies. Promoters of the Paleo diet or “caveman diet” suggest that such diseases could be prevented in large part by returning to a diet that is more in sync with our metabolic machinery than is the typical modern Western-style diet. Nutrition research does increasingly indicate that many aspects of the modern diet do in fact contribute to the development of cardiovascular disease (CVD), obesity, type 2 diabetes (DM), and numerous other modern diseases. The high sodium to potassium ratio of a modern diet certainly contributes to elevated blood pressure and CVD. The intake of calorie-dense foods loaded with refined carbohydrates and/or refined fats and oils certainly contributes to the development of obesity and type 2 DM.Where Paleo diet proponents seem out of sync with research data is in their claim that diets high in animal products and especially those not fattened up on grains do not promote atherosclerosis and CVD. They argue that CVD was rare before people started farming and started consuming grains and animals fattened on grains and point to data from modern-day humans living something akin to a hunter-gatherer lifestyle who often have less CVD than people living in modern societies, despite a sometimes high intake of animal products. Many Paleo diet proponents even advocate foods high in saturated fat and/or cholesterol such as coconuts and eggs from range-fed chickens, claiming that such foods do not promote atherosclerosis. Like Atkins and other proponents of low-carbohydrate diets, many Paleo-dieters blame atherosclerosis on too much carbohydrate, even when that carbohydrate is coming from whole grains and beans.An article published in the March 10, 2013 edition of the Lancet seriously undermines the popular mythology that a diet high in hunted and gathered foods will prevent coronary artery disease. Researchers examined mummified human remains, including some from hunter-gatherer cultures whose diets were devoid of grains. They also looked at the mummies of ancient Egyptians, who consumed whole grains but no refined grains or sugars. The 138 mummified bodies all came from cultures where plenty of animal products were consumed, so their intake of saturated fat and cholesterol was likely rather high. Unfortunately for the Paleo diet advocates the mummies from all these ancient cultures showed clear evidence of calcified arteries (indicative of advanced atherosclerotic lesions) despite an estimated age of death of only 43yrs. If these mummified remains were representative of human populations many years ago, then this data is inconsistent with the belief that grains, beans, and refined sugars were the main cause of atherosclerosis during the Paleolithic period. This data suggests that the consumption of meat and other animal foods are largely responsible for promoting atherosclerosis.The Paleo diet promoters most often point to Eskimos as an example of a human population that consumes a diet high in saturated fat and cholesterol and yet experience little or no atherosclerotic disease. However, the notion that the incidence of CVD was low among Eskimos subsisting on a traditional diet composed largely of marine animals while achieving almost axiomatic status among Paleo dieters is suspect. Indeed, the scientific evidence for this is weak and rests on early clinical observation and very uncertain mortality statistics. Autopsy data has clearly shown atherosclerosis is very common among Inuit and other Eskimo cultures. However, the now decreasing trend in mortality from CVD among Inuit populations who are undergoing rapid Westernization of their diet with increasing amounts of refined grains and sugar-rich foods suggests that the replacement of fatty animal products with even refined grains and sugars is lowering their LDL-C levels and reducing deaths from CVD. The scientific evidence for the most part appears to support the current prevailing theory about what aspects of the diet are largely responsible for promoting atherosclerosis. The now widely-accepted lipid hypothesis postulates that the primary cause of atherosclerosis is a diet high in saturated fat and cholesterol, which come primarily or entirely from animal products, respectively.Bottom Line: Some aspects of the Paleo diet, such as the low sodium/potassium ratio, have credible scientific support but the now widespread belief among Paleo theologists that CVD is largely promoted by the intake of carbohydrates (including from their perspective even whole grains and legumes) rather than an excessive intake of animal foods high in saturated fat and cholesterol is without scientific merit. Indeed, even when the dietary saturated fat and cholesterol are derived almost entirely from omega-3 rich seafood, the scientific evidence shows that it will raise LDL-cholesterol levels and promote coronary artery disease. This Ted video with Christina Warinner, Ph.D. an archeologist does a nice job of debunking a variety of Paleo-Diet myths: https://goo.gl/wFnio4.By James J. Kenney, PhD, FACNReferences: 

1.  Eaton SB, Eaton SB 3rd, Konner SJ. Paleolithic nutrition re-visited: a twelve year retrospective on its nature and implications. Euro J Clin Nutr.1997;51: 207–16
2. Thompson RC, et al. Atherosclerosis across 4000 years of human history: the Horus study of four ancient populations. http://dx.doi.org/10.1016/S0140-6736(13)60598-X.
3. Bjerregaard P., et al. Low incidence of CVD among the Inuit - what is the evidence? Atherosclerosis.2003;166:351-7.
4.  http://www.nhlbi.nih.gov/guidelines/cholesterol/atp3full.pdf