Protein Power Lifeplan: A New Comprehensive Blueprint for Optimal Health

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Chapter One

Man the Hunter

The deviation of man from the state in which he was originally placed by nature seems to have proved to him a prolific source of diseases.

—Edward Jenner (1749-1823)

In our living room on the coffee table sits one of our most prized possessions, a fifteen-to-twenty-thousand-year-old cave-bear skull that we got from Russia. From back of the head to snout the skull measures almost two feet in length and sports canine teeth that are three inches long. The entire animal would have been about seven to eight feet tall and weighed close to a thousand pounds. Examination of this skull shows a huge ridge running along the top, where the muscles that worked the jaws were connected. From here they ran along the face and attached to bony protrusions (called the mandibular ramis) on the lower jaw. The larger the mandibular ramus, the greater the mass of the muscle attached to it and the greater the closing force of the jaws. The mandibular rami of our cave bear are about the size of a child's hand, and when you compare them to the size of the rami of a human jaw, or even a dog's jaw, which are both about the size of a dime, you can imagine the crushing strength in the jaws of this creature.

Cave bears used to roam the fields and forests of prehistoric Europe, until they were hunted to extinction by early man. As we gaze at our skull and envision the eight-foot, thousand-pound beast with the three-inch teeth, the four-inch claws, and the jaw strength to snap a man in two, we can begin to appreciate how great our primeval ancestors' need for meat musthave been. To think of this creature, snarling and gnashing its teeth, slashing with giant claws, charging and roaring, it almost defies imagination that people just like us went after them with not much more than sharpened sticks. But they did, and did it so well that cave bears are no more. And we are still here and carry in our genes this same need for meat that drove our forebears to brave tooth and claw to get it.

Despite these facts, we still regularly receive letters that question exactly what kind of diet our ancient ancestors actually ate. Although in anthropological scientific circles, there's absolutely no debate about it—every respected authority will confirm that we were hunters—many people still believe in the "dangers" of meat eating in light of our supposed vegetarian past. We've had at least twenty people send us copies of the same table published in an anti-meat book from the 1970s showing how sundry parts of our anatomy or physiology are more like those of herbivores than of carnivores, thus "proving" our vegetarian inclinations. We are, of course, neither. We're omnivores, able to subsist on meat and plants—hence the intermediate size of our intestinal tracts. Recently we received a newsletter clipping quoting a well-known doctor on the subject of our vegetarian past, as well as an e-mail from a Protein Power devotee in Italy whose physician had forbidden him to eat meat because it was "a silent poison." We even had one indignant reader tell us in no uncertain terms that she was abandoning our program unless we could answer to her satisfaction the questions that were raised by the quote, boldly circled in red, in her church bulletin, which she enclosed. The little blurb pronounced with great authority that the human body was designed to eat only food of plant origin and that meat "putrefies" in the human colon, becoming a poison. The physician from the (as always) prestigious medical school who had made this statement was someone totally unknown to us, and after a diligent search, we discovered he had been dead for over a hundred years. Such are the myths and misconceptions about what we humans were designed to eat.

Our meat-eating heritage—a topic we thought we'd covered sufficiently in our previous book—is an inescapable fact. But to be certain that this time we leave no room for doubt, we will delve back into the issue more deeply and lay out the facts of the matter so that you'll be armed with the truth and prepared to defend your nutritional choice with authority.

You'll hear it said, usually by those espousing vegetarianism for ideological reasons, that primitive tribes that eat a mainly plant-based diet enjoy better health. For instance, such authorities frequently cite the lower-than-the-average-American cholesterol levels of a typical male of the !Kung tribe (a commonly studied, contemporary chiefly vegetarian hunter-gatherer society) as proof of the health benefits of meatless living. While it's true that some predominantly vegetarian hunter-gatherer groups (a minority of such groups, as we shall see later) have low rates of the "chronic diseases of affluence," it doesn't necessarily follow that this good fortune is a result of their diet. Consider the Masai, for example. The Masai, another intensively studied group of African pastoralists who subsist mainly on meat, milk, and the blood of the cattle they herd, are famous and famously studied because of their incredibly low cholesterol and blood pressure levels even into advanced age despite their enormous intake of fat. Here we've got two totally diverse diets—the !Kung and the Masai—and the followers of both have a low incidence of chronic diseases. Obviously there are other factors at play in the development of these diseases besides just diet, so let's take a closer look at the issue.

Anthropologists have known for decades that the health of humanity took a turn for the worse when our ancestors abandoned their hunter-gatherer means of subsistence in favor of the farm somewhere between eight-thousand and ten-thousand years ago. The fossil record leaves little doubt that compared to their farming successors, the hunters were more robust, had greater bone density, decreased infant mortality, a longer life span, a lower incidence of infectious diseases and iron-deficiency anemia, fewer enamel defects, and little or no tooth decay.

Humans have followed a Paleolithic diet for a few million years and a "modern" agricultural diet for only a few thousand years. The not too gentle forces of natural selection have spent millennia shaping and molding our evolving line, weeding out those offshoots and mutations that didn't thrive on the available fare, reinforcing those traits that improved our survival, until we emerged as modern humans some one-hundred-thousand years or so ago. Since our modern form and physiology today is the same as that of these one-hundred-thousand-year-old ancestors, it stands to reason that we should function best on the diet they—and we, their descendants—were designed to eat, not necessarily the "prudent" diet recommended by modern nutritionists, which is often composed primarily of foods that weren't even in existence for the vast majority of our time on earth. It is by turning to the vast amount of anthropological data that we can determine what our ancestors ate for the three to four million years that we have been recognizable as humans.

In a Word: Meat

In anthropological research if you follow the trail of meat consumption, you'll find the history of our earliest ancestors, because there is no real debate among anthropologists about early man's history as a meat eater and his evolution into a skilled hunter; the only debate is about when this hunting ability became fully developed.

Upon the discovery of the first fossils of our earliest upright ancestors anthropologists postulated that these creatures, the australopithecines, and those that followed until the advent of agriculture was "bloodthirsty, savage" hunters. As archeologists developed more technologically sophisticated means of analyzing their collections of bones and tools, thinking drifted from the idea of early man as hunter to that of early man as scavenger. Gone was the notion of groups of skilled hunters stalking, bringing down, and butchering large herbivores; in its place was the vision of groups of hominids coming upon the kills of large carnivores and stripping the remaining bits of flesh from the carcasses and using primitive tools to pummel and break into the cavities of the long bones and skulls to get at the marrow and brains within. The mainstream archeological and anthropological view posits that this scavenging lifestyle predominated until the last one-hundred-thousand years or so, coinciding with the arrival on the scene of anatomically modern humans. But, thanks to recent findings, this view is changing—and changing in almost flashback fashion to the ideas of the earlier anthropologists. Our ancestors from a long, long way back indeed appear to have been skilled hunters.

New excavations in Boxgrove, England, and Atapuerca, Spain, reveal that hominids as far back as five-hundred-thousand or more years ago were exquisitely skilled hunters. Archeologists at Boxgrove found evidence of numerous kill and/or butcher sites of extinct horses, rhinoceroses, bear, giant deer, and red deer—all large mammals requiring a great deal of skill and fortitude to bring down with primitive implements. Researchers know these animals were hunted and not just found and scavenged, not only because of the arrangement of bones at the butcher site, but through microscopic evidence as well. When analyzed under a microscope, the bones of scavenged carcasses typically show the cut marks from the tools of the scavengers lying over the tooth marks of the carnivores that actually made the kill, indicating that the scavenging came later. At Boxwood, archeologists found just the opposite. The cut marks from the flint tools on the bones show evidence that tendons and ligaments were severed to remove muscles from the bones. The cut marks compare to those produced by today's butchers using modern tools. In the words of Michael Pitts and Mark Roberts, two of the primary excavators at Boxgrove, "every animal for which there is any evidence of interference by the hominids has been carefully, almost delicately, butchered for the express purpose of consuming the meat."

Further evidence of hunting comes from several actual wooden spears found throughout Europe that have proven to be the oldest wooden objects of known use found anywhere in the world. Archeologists have dated an almost sixteen-inch-long spear tip carved of yew wood found in 1911 in Clacton, England, to be somewhere between 360,000 and 420,000 years old. Another spear, also made of yew, that is almost eight feet long and dated to 120,000 years old was found amid the ribs of an extinct elephant in Lehringen, Germany, in 1948. A few years ago excavators in a coal mine near Schöninger, Germany, found three spruce wood spears shaped like modern javelins, the longest of which measured over seven feet, that proved to be 300,000 to 400,000 years old. And at one of the butcher sites at Boxgrove, excavators actually found a fossilized horse scapula that shows what appears to be a spear wound.

The excavation at Boxgrove provided archeologists with another surprise. It had long been thought that such stone tools as arrowheads and hand axes, once fashioned, were carried around by their makers and used as needed, much as we do today with modern hunting knives and other camp tools. Researchers who have practiced making prehistoric tools and arrowheads from flint—flint knapping, as it's called—found the task tedious, difficult, and fraught with the constant risk that one wrong strike could destroy the tool in the making. As a result, the thinking was that the effort put into making quality stone tools was so great that the makers would surely value them and keep them as long as they could. Amazingly, it appears from the meticulous examination of these ancient sites that these hominid hunters were so adept at making flint tools for butchery that they knocked them off on the spot, used them to skillfully dismember their prey, and left them at the site rather than carry them around. And these weren't just crude flint chips; these were some of the finest flint hand axes ever found. Modern attempts to reproduce the quality of these tools have usually fallen far short of the mark. Obviously these ancient hominids were skilled enough to whip out a flawlessly made butchering tool at a moment's notice, a fact that implies a lifetime of hunting, butchering, and meat consumption.

We know from these European sites that hominids were actively hunting and eating meat as far back as five-hundred-thousand years ago, but what about before that? The earliest stone tools date to around 2.6 million years ago and have been found in association with extinct animals' bones from the same period. Some of these have cut marks with overlying carnivore teeth marks, indicating hunting, while others have carnivore teeth marks with overlying cut marks, implying scavenging. The most probable conclusion is that protohumans back at least 2.6 million years ago—a time corresponding to the appearance of the genus Homo—were engaged in the consumption of meat by either scavenging or hunting activities and probably a combination of the two.

Prior to 2.6 million years ago the human line was represented by australopithecines, which have been believed to be primarily fleshy fruit eaters. So, it was thought, the human line developed the taste for meat sometime between the plant-eating australopithecines and the appearance of Homo, but even that time frame has now been pushed back. Anthropologists Matt Sponheimer and Julia Lee-Thorp from Rutgers University and the University of Cape Town, respectively, performed an ingenious analysis on the remains of four three-million-year-old Australopithecus africanus specimens found in a cave in South Africa. Bones of this age are always fossilized, thus preventing researchers from extracting living material from them for analysis, but not so for the tooth enamel; tooth enamel persists relatively unchanged through the millenia and lends itself to testing for organic content. Whatever is incorporated into the developing enamel stays there—in this case for three million years. By testing for variations in the carbon atoms making up the tooth enamel researchers can determine what the owner of the tooth ate because different food sources contain specific carbon isotopes. When Sponheimer and Lee-Thorp analyzed the australopithecine enamel for the content of Carbon-13, a heavy isotope typically found in grasses and in the flesh of grass-eating animals, they found plentiful amounts, indicating that these hominids ate either a fair amount of grass or grass-eating animals or both. Analysis of the surfaces of the teeth, however, didn't show the specific scratches that are the telltale signs of grass eaters, leading the researchers to conclude that australopithecines at least as far back as three million years ate meat.

We have evidence tracking back three million years for meat eating by our ancestors and at least a five-hundred-thousand-year history of skillful hunting. In terms of generations this means that we modern humans are the result of one-hundred-fifty-thousand generations of meat eating, twenty-five-thousand generations of skilled hunting, but only a mere four-hundred to five-hundred generations of agriculture. Since geneticists calculate that it takes at least two-thousand generations for even minimal changes to be manifest, it should be apparent that eons of meat eating forged our physiology and metabolism to respond optimally on a diet containing significant amounts of meat. A low-fat, high-carbohydrate diet, the real fad diet in evolutionary terms, limits the consumption of the meat we were designed by nature to eat and replaces it with starchy foods that our bodies haven't had the time to adapt to. It's no wonder the low-fat diet wasn't what it was cracked up to be. It's far too new for our bodies to know what to do with.

Brain Food

Not only was meat a principal source of nutrition for developing man, it actually was the driving force allowing us to develop our large brains. For years anthropologists argued that we humans got our large brains because we had to develop them to learn hunting strategies to capture and kill game much larger, faster, and meaner than ourselves. Anthropologists Leslie Aiello and Peter Wheeler turned that idea on its head in a brilliant paper postulating that we were able to develop our large brains not to learn to hunt but because the fruits of our hunting—nutrient-dense meat—allowed us to decrease the size of our digestive tracts. The more nutrient dense the food, the less digestion it needs to extract the nutrients, and consequently the smaller the digestive tract required. (The human digestive tract, while longer than true carnivores, is the shortest of any of the primates.)

Is meat really that nutritionally dense? Let's take a look at a few examples of meat compared to plant foods and see. First, let's look at protein. Protein is the only true essential macronutrient. Fat is also essential, but you can go a lot longer without fat than you can without protein. (Carbohydrates, the third macronutrient, are totally unessential to human health.) So, if you are trying to get protein you could eat 8 ounces of elk meat, a small amount by Paleolithic standards, and get about 65 grams of it. Or you could eat almost 13 heads of lettuce to get the same amount. Or 56 bananas or 261 apples or even 33 slices of bread. If you're trying to get methionine, an essential amino acid that the body uses to make glutathione, its major antioxidant, you could eat the same 8 ounces of elk, or you could eat any of the following: 22 heads of lettuce, 127 bananas, 550 apples, or 46 slices of bread. In almost any nutrient category you want to look at, meat is going to come out a winner because of its incredible nutritional richness that doesn't require much digestive activity to get to.

Table 1.1 shows the difference between the digestive tract of a sheep, which is a true herbivore, and a dog, which is primarily a carnivore, and a human. Let's take a look and see where our species falls in the spectrum from carnivorous to vegetarian traits.

But What If I'm a Vegetarian?

A larger percentage of our patients than you might imagine are vegetarian to some degree. With some modifications, the Protein Power LifePlan works fine for vegetarians, but before we start patients on the vegetarian version we always inquire as to their rationale for following such a diet. If they are vegetarians because they believe it a more healthy way to eat, we disabuse them of that notion quickly. If, on the other hand, they are vegetarians for ideological reasons, we have no quarrel with that and we help them modify our program to solve their health problems within the limits of their ideology. We do, however, encourage them to read a fascinating little book entitled The Covenant of the Wild that goes a long way toward removing many of the inhibitions that some people have about using animals for food.

Were We Hunter-Gatherers or Gatherer-Hunters?

What about the gathering that went along with the hunting? Don't we have a history of a fair amount of plant consumption along with our meat eating? How about the ancient potatoes that went along with our mastodon steak? Until the advent of fire about five hundred thousand years ago, it was fairly difficult for our predecessors to get enough calories from plant foods because the plants themselves fought back by evolving anti-nutrients. Anti-nutrients are chemicals within the plants that bind with the nutrients, making them unavailable for absorption by potential herbivorous predators. (See chapter 6, "The Leaky Gut: Diet and the Autoimmune Response," for more details.) Often we lose sight of the fact that, like humans and other species, plants evolve, too. The inner goal of plants is to live long, prosper, and disseminate as many seeds as possible in order to propagate the species. If a particular plant is tasty and easy to harvest (we're talking about plants in the wild, not hybrid plants that we put in gardens today), it doesn't last long and certainly doesn't get much of a chance to spread its seeds. Plants, however, that develop (via natural selection) a means to keep from being eaten, whether by growing protective thorns or stickers, acquiring a particularly nasty taste, or producing anti-nutrients, survive to reproduce and multiply. The variety of plant foods available to the vast majority of evolving humans simply wasn't enough to nourish them without a generous amount of meat in the diet. In fact, Cambridge anthropologist Robert Foley says that hunter-gatherers "along with modern agriculturalists . . . are an evolutionarily derived form that appeared towards the end of the Pleistocene [ten thousand or so years ago] as a response to changing resource conditions." In other words, according to Dr. Foley, gathering, like agriculture, is a recent phenomenon, not a lifestyle that has its roots in several million years of evolution. That said, it's interesting to find, however, that hunter-gatherers (low-fat proponents always want to call them gatherer-hunters) are primarily meat eaters.

Most of the commonly accepted information about hunter-gatherers comes from a paper by R. B. Lee that was presented at a 1968 symposium in Chicago called, strangely enough considering the data presented, "Man the Hunter." Using the 1967 edition of Murdock's Ethnographic Atlas, a compilation of data about 862 of the world's societies, Lee concluded that the average hunter-gatherer got about 65 percent of his calories from plants and the remaining 35 percent from animals. This paper with its 65:35 plant-to-animal-food ratio has been quoted extensively in both the medical and the anthropological literature and used as the basis for the calculations of the prehistoric diet by innumerable authors who have promoted the idea that the diet of evolving man was mainly plant based. Unfortunately it is incorrect.

A colleague and good friend of ours, Loren Cordain, Ph.D., professor at Colorado State University, one of the world's experts on the Paleolithic diet, and one of the most industrious human beings we've ever known, sensed that there was something not quite right about Lee's paper and decided to investigate the data himself. Dr. Cordain's first clue that something was amiss was unbelievably basic and had been overlooked by all the researchers who had used Lee's paper as the basis of their own work. He simply ran a computerized nutritional analysis of a typical hunter-gatherer diet using the 65:35 plant-to-animal-food ratio. He discovered that for a human to get the calories needed to live on a diet of this nature using plants commonly available to a hunter-gatherer, he would have to gather approximately twelve pounds of vegetation daily, an unlikely scenario, to say the least.

After making this discovery, Dr. Cordain reviewed Lee's original paper and calculations and unearthed some startling facts. Lee only used 58 of the 181 hunter-gatherer societies listed, and he didn't include animal foods obtained from fishing in his calculations. Moreover, he classified the collection and consumption of shellfish as a gathering activity. The Ethnographic Atlas itself considers the collection and consumption of small land fauna (insects, invertebrates, small mammals, amphibians, and reptiles) gathering and categorizes them as such, in so doing ascribing many of the actual animal-derived calories to the plant category.

Dr. Cordain turned to the 1997 update of the Ethnographic Atlas, which represents 1,267 of the world's societies, 229 of which are hunter-gatherers, and did his own calculations. Using all the hunter-gatherer societies listed and putting fishing and shellfish gathering into the appropriate hunter category, he found that the 65:35 values of Lee were flipped. Dr. Cordain calculated the actual plant-to-animal-food ratio to be 35 percent plant, 65 percent animal. He found that the majority of hunter-gatherers throughout the world get over half their subsistence from animal foods, while only 13.5 percent of the world's hunter-gatherers derive more than half their food from gathering plants. And these figures would lean even more in the direction of animal food were it not for the bias built into even the updated Ethnographic Atlas by the inclusion of small animals, reptiles, worms, grubs, etc., in the plant category.

Our primitive ancestors, whether hunters or hunter-gatherers, by all accounts lived fairly prosperous lives, at least by their standards. They lived in small, closely knit groups, and compared to the early farmers that followed them, they had much better health, greater stature, more children reaching maturity, and a longer life span. Turning to an agricultural existence forced the reliance on fewer numbers of foods, and since no single plant food provides a full complement of all the nutrients humans need, many people suffered nutritional deficiencies. And if the crop failed, famine set in—an experience foreign to most of the hunter-gatherer populations because they were always on the move, traveling to where there were plenty of game and fertile fields for gathering. A system in which large groups of people lived in close proximity, at least where early man was concerned, wasn't really all that advantageous. Most of the infectious diseases that have caused so much misery throughout history—smallpox, cholera, tuberculosis, and a host of other bacterial and viral infections—became problems only after the advent of the agriculture and the development of cities. All this begs the question, why did humans ever settle down and become civilized? Why did they leave their Garden of Eden, give up their hunting jobs requiring only a few hours of work per day, and submit to the backbreaking toil of an agricultural life? It just doesn't make sense.

This question has been pondered ever since anthropologists figured out that humans made this transition, and, as you might expect, almost as many hypotheses have been forwarded as there are anthropologists. Greg Wadley and Angus Martin, researchers at the University of Melbourne in Australia have put forth an engaging theory that makes a lot of sense to us. They point out that there exists a considerable amount of research establishing the fact that cereal grains, especially wheat, maize, and barley and, to a slight extent, dairy products contain opioid substances called exorphins. Opioid substances are those that have an opium-like effect, stimulate the opioid receptors in the brain, and are to varying degrees addictive. When bands of primitive people stumbled onto patches of wild grains and consumed them they discovered the reward from consuming "addictive" substances, i.e., comfort foods. People quickly developed ways of making these foods even more edible by grinding and cooking them. As the grains become more palatable through processing, the more they were consumed and the more important the exorphin reward became.

In the words of Wadley and Martin, "At first, patches of wild cereals were protected and harvested. Later, land was cleared and seeds were planted and tended, to increase quantity and reliability of supply. Exorphins attracted people to settle around cereal patches, abandoning their nomadic lifestyle, and allowed them to display tolerance instead of aggression as population densities rose in these new conditions." According to these researchers, then, grains were the first opiate of the masses!

Whether this theory is the correct one or not, there is no question in our minds that carbohydrate foods cause cravings and are, to a certain degree, addictive, particularly those of cereal grain origin. If you look at any list of the top ten foods consumed by Americans you will find bread, crackers, chips, breakfast cereals, and other high-carbohydrate, grain-based products. We have all experienced the addictive nature of carbohydrates and their ability to override the feeling of fullness. Think back to the last time you were at a restaurant or at someone's house for dinner and you ate until you were stuffed. If one of your dinner mates asked you to try just a bite of the delicious swordfish (or any other meat dish), you no doubt begged off, saying, "I'm just too full; I couldn't possibly eat another bite." But then, if your host or your waiter arrived bearing dessert, you probably said, "Oh, well, dessert, sure. I'll have some cake"—or ice cream, or tiramisu, or cobber, or whatever. You are able to eat the dessert, which is always rich in carbohydrates, because just the thought of the carbohydrates overrides your brain signals telling you that you're full. Carbohydrates seem to trigger no off switch. That's why people who binge always do so on carbohydrates. No one binges on steak or eggs or pork chops; they always binge on cookies and candies and other carbohydrate junk foods. Having taken care of as many carbohydrate junkies as we have over the past fifteen years, it is clear to us that cereal grains and products made from them have an allure that transcends the mere taste bud stimulation they provoke. As Wadley and Martin point out, "The ingestion of cereals and milk, in normal modern dietary amounts by normal humans, activates reward centres in the brain. Foods that were common in the diet before agriculture . . . do not have this pharmacological property. The effects of exorphins are qualitatively the same as those produced by other opioid . . . drugs, that is, reward, motivation, reduction of anxiety, a sense of well-being [i.e., comfort foods], and perhaps even addiction. Though the effects of a typical meal are quantitatively less than those of doses of those drugs, most modern humans experience them several times a day, every day of their adult lives."

It should be clear by now that whichever way you look at it, the majority of our time as humans or our sort-of-human predecessors on this earth has been spent eating meat. The adoption of agriculture with its dependence on a grain-based diet is a recent phenomenon, in fact just a second in evolutionary time. The forces of natural selection haven't yet had anywhere near the time necessary to mold us to function optimally on a grain-based diet. We are still operating with forty-thousand-to-one-hundred-thousand-year-old biochemistry and physiology. Geneticists have evaluated the DNA sequences of humans and our closest relatives, the chimpanzee, and found the difference to be a mere 1.6 percent of genes, meaning we have 98.4 percent of genes in common with chimpanzees. By determining the rate of genetic change since we split away from chimpanzees, scientists have been able to calculate the rate of genetic mutation in humans, which turns out to be on the order of about a half a percent per million years. That means that over the past ten thousand years—the time since the advent of agriculture—we have changed genetically to the tune of about 0.005 percent. That's not much at all. In fact, that means that we have 99.995 percent of our genes identical with those of our big game-hunting ancestors. We are they. We have Fred Flintstone bodies living in a George Jetson world. And therein lies the root of our problems.

In our medical/nutritional practice we view modern diseases in our patients through the lens of their Paleolithic ancestry and use the Paleolithic diet and lifestyle with some twentieth-century modifications as a template to restore their health. (Throughout this book, we'll hold up that lens to the Paleolithic world to give you a look at where and how your modern lifestyle and diet may conflict with it.) We care for patients who have heart disease, elevated cholesterol and triglyceride levels, diabetes, obesity, high blood pressure, gastroesophageal reflux, various autoimmune disorders, and a number of other problems by using a protein-based diet containing a fair amount of meat. Patients are constantly amazed at how quickly they improve and often believe that it is nothing short of miraculous. The reality is that we are just getting them to follow a diet they were intended to eat. We were designed to function optimally on a particular diet, we stray from this diet, we develop disease, we return to the correct diet, and the disease disappears. It's basically as simple as that.

One of the primary ways in which a Paleolithic nutritional regimen works to resolve these problems is by lowering insulin levels. Virtually every food our prehistoric ancestors had available (with the exception of honey) is one that doesn't stimulate the body to produce much insulin, whereas the vast majority of foods we eat in today's world do just the opposite and send insulin levels through the roof. In the next chapter we'll take a look at this most powerful of our metabolic hormones and learn the havoc it can wreak when we stray from our ancestral bill of fare.

BOTTOM LINE

The overwhelming mass of scientific evidence supports the notion that for most of our time on earth, humans and their pre-human ancestors have eaten meat. By all reputable scientific accounts, we've been hunting and gathering (with heavy reliance on the hunting) for the better part of three million years. Eons of natural selection and human development molded our metabolic machinery to succeed on this ancient dietary scheme that appears to have included about 65 percent foods of animal origin and about 35 percent foods of plant origin. Only about ten thousand years ago (at most) did we settle down to cultivate grains and begin to include them as food in our diets. The metabolic changes necessary for humans to adapt to this dietary change—in short, to be able to use these "new" foods well—would reasonably take a few thousand generations (or about forty thousand or fifty thousand years). We're simply not there yet—and won't be anytime soon.

Turning to the use of grains allowed humans to settle in large cooperative groups necessary to build great civilizations, but at a price to the individual members of the group. While we can subsist on grain-based diets, we don't as a species thrive on them; the fossil record shows that after the adoption of agriculture human health, stature, and longevity went into sharp decline. In the last century in the Western world, thanks to a general increase in dietary protein, we've begun to recover our stature, but because of our continued heavy reliance on cereal grains, metabolic health still lags. We're riddled as a society with epidemics of diabetes, high blood pressure, heart disease, and obesity, all of which we inherited when our ancient ancestors abandoned their successful hunting-and-gathering lifestyle in favor of the addictive lure of grains (components of which indeed do stimulate the narcotic centers of the human brain).

In our medical/nutritional practice, we care for people with all components of this epidemic of modern diseases. To restore their health, we advocate a return to the basic nutritional principles of our ancestral hunting-gathering lifestyle by prescribing a diet of nutrient-dense foods—meat, fish, and poultry, rich in protein and good-quality essential fats; fruits, berries, and vegetables, rich in antioxidants and cancer-fighting substances—and limiting what early humans never knew existed—grains, refined sugars, and other concentrated starches.