THE PALEOLITHIC DIET
The Paleolithic Diet is an ancient way of eating that has been around ever since the ‘dawn of man’ during the Paleolithic period, a period of about 2.5 million years that ended about 10,000 years ago. The Paleolithic diet, also known as the paleo diet, the caveman diet, or the hunter-gatherer diet recommends that you eat what the caveman ate, which consisted primarily of an omnivorous diet of: wild meat and fish, fruits, vegetables, nuts and berries. The foods included in this diet are those that the cavemen could hunt, scavenge, or gather and that could be eaten without cooking - since fire is a recent invention in the evolutionary period of the human diet and digestive system.
This ancient dietary eating pattern has re-emerged and has gained popularity since the mid 1970’s. Proponents of this diet believe that processed foods are responsible for causing diseases such as cancer, heart disease, arthritis and other immunologic conditions, as well as unintentional weight gain (increased body fat).
In its more modern, nutritionally conscious and practical form, the diet consists of consuming: animal protein from wild and domesticated, but naturally-fed and/or grass-fed, animal and fish sources, which contain higher amounts of omega 3 essential fatty acids than grain-fed livestock. In addition, animal protein is the cornerstone of every meal and is accompanied with small to large amounts of wild and cultivated: berries; other fruits; green leafy vegetables; watery vegetables ( i.e., celery); root vegetables (i.e., carrots); nuts and seeds; water and green or herbal teas to drink.  Unlike raw food diets, the foods in this modernized version of the Paleolithic diet may be cooked. Cooking is widely accepted to have been practiced 250,000 years ago in the Middle Paleolithic era, and possibly as long ago as 500,000 years ago. 
The diet excludes: any grain-based carbohydrate items, such as those from: corn, rice, or wheat; legumes; dairy products; refined salt and sugar; and processed refined oils. The study of Paleolithic nutrition is based upon the theory that modern humans are genetically tailored to the traditional diet of their Paleolithic ancestors and that human genetics have been negatively altered since the dawn of agriculture.
In the modern Paleolithic diet, the average protein intake is around 35% of total calories; average carbohydrate intake is around 40% of total calories, and the average fat intake is around 25% of total calories, with saturated fat intake fluctuating between approximately 10% to 20% of total calories depending on whether the Paleolithic diet participant consumes more or less fish, poultry, and/or red meat for the animal protein portion of their diet. 
Pros: Some of the benefits from implementing a modern Paleolithic diet include the fact that the fresh fruits, vegetables, lean meats, and wild fish that make up the this diet are more nutrient-dense with higher levels of vitamins, minerals, phytochemicals, and omega 3’s with no or less toxic food manufacturing by-products, verses the typical western or standard American diet of refined sugars, grains, refined dairy products, and refined oils and other fat by-products. In fact, more than 70% of the total daily energy consumed by all people in the United States comes from these ‘industrialized foods’ and researchers and supporters of the Paleolithic diet argue that excessive consumption of these common western foods are responsible for the current epidemic levels of obesity, cardiovascular disease, high blood pressure, type 2 diabetes, osteoporosis and cancer in the US and other contemporary western populations, and therefore eating the opposite of this standard American diet ( or S.A.D.) will minimize or prevent the aforementioned negative health conditions 
Other reasons that The Paleolithic Diet is thought to be such a healthy way of eating, and that it is believed to assist in minimizing or delaying the degenerative diseases mentioned above, is due to the diet’s: high fiber, from increased fruit and vegetable carbohydrate intake; low glycemic make up; high potassium to low sodium ratio; low acidity, high alkalizing properties; gluten-free, casein-free, soy-free, and thus low allergenicity potential; and its lower ‘anti-nutrient’ content.  In fact, the first animal experiment on a Paleolithic diet suggested that this diet, as compared with a cereal-based diet, conferred positive health markers, such as: higher insulin sensitivity, lower C-reactive protein and lower blood pressure in 24 domestic pigs. There was no difference in basal serum glucose. The first human clinical randomized controlled trial involved 29 people with glucose intolerance and ischemic heart disease and it found that those on a Paleolithic diet had a greater improvement in glucose tolerance compared to those even on a Mediterranean diet. 
*Note: Under the traditional lifestyle of the Paleolithic era as well as current epidemiological studies of present day hunter-gatherer tribes, such as the Masai, Tokelua and Pukapuka tribes, individuals that practice a Paleolithic diet were extremely active physically in terms of the hunting and gathering for food daily, so that may also account for some of the health benefits of The Paleo diet. 
Cons: There are at least a few arguments brought up against implementing a Paleolithic diet in terms of health and obstacles based on of our modern economy. They include: too high of percentage of cholesterol intake from an animal-based and seafood-based hunter-gatherer diet and/or too high of percentage of saturated fat from an animal-based hunter-gatherer diet, to be cardio-protective.  In addition, it may be a difficult diet to implement on a worldwide scale. According to Loren Cordain, an expert and advocate of The Paleo diet, if such a diet was widely adopted, it would compromise the food security of populations dependent on cereal grains for their subsistence.   Barry Bogin, a professor of anthropology at the University of Michigan, states that less intensive farming techniques, such as pasture-grazed (generally healthier, grass-fed, omega 3 containing) cattle, would not produce sufficient meat to feed the world’s population. 
Paleontological evidence verifies that humans have always been omnivores, therefore hunters and gatherers, and not solely vegetarians.
What kind of "evidence" are we talking about here?
At its most basic, an accumulation of archaeological excavations by paleontologists, ranging all the way from the recent past of 10,000-20,000 years ago back to approximately 2 million years ago, where ancient "hominid" (meaning human and/or proto-human) skeletal remains are found in conjunction with stone tools and animal bones that have cut marks on them. These cut marks indicate the flesh was scraped away from the bone with human-made tools, and could not have been made in any other way. You also find distinctively smashed bones occurring in conjunction with hammerstones that clearly show they were used to get at the marrow for its fatty material.
Prior to the evidence from these earliest stone tools, going back even further (2-3 million years) is chemical evidence showing from strontium/calcium ratios in fossilized bone that some of the diet from earlier hominids was also coming from animal flesh. (Strontium/calcium ratios in bone indicate relative amounts of plant vs. animal foods in the diet. Scanning electron microscope studies of the microwear of fossil teeth from various periods well back into human prehistory show wear patterns indicating the use of flesh in the diet too.  The consistency of these findings across vast eons of time show that these were not isolated incidents but characteristic of the behavior of hominids in many times and many places. To anyone who really looks at the published evidence in scientific research and peer-reviewed journals, and has a basic understanding of the mechanisms of how evolution works, there is really not a whole lot to be controversial about with regard to the very strong evidence indicating that flesh has been a part of the human diet for vast eons of evolutionary time. The real controversy in paleontology right now is whether the earliest forms of hominids were truly "hunters," or more opportunistic "scavengers" making off with pieces of kills brought down by other predators, not whether we ate flesh food itself as a portion of our diet or not.
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