In evolution, speciation results from to specialization in exploitation of a particular ecological niche.
Our closest primate relatives, the chimps and gorillas, chose to exploit specific ecological niches which exerted natural selection pressures that resulted in modern chimps and gorillas having bodies specialized for eating largely vegetarian diets, in ways that make each a unique species.
Human ancestors chose to exploit a very different ecological niche which exerted natural selection pressures that resulted in modern humans having bodies specialized for a largely carnivorous diet. Basically, they chose a habitat in which plant foods were scarce and animal foods – starting with insects, worms, etc. – were more abundant.
I don’t deny that we have the ability to consume plant foods. I only emphasize that whereas other primates have specialized in eating vegetation, humans have specialized in eating meat. We have specialized to the extent that we can live on meat alone, and doing so can improve our health.
Adventures in Diet
In the November 1935 issue of Harper’s Monthly Magazine, in his first installment of a series of three articles entitled Adventures in Diet, Vihljalmur Stefansson wrote
“Not so long ago the following dietetic beliefs were common: To be healthy you need a varied diet, composed of elements from both the animal and vegetable kingdoms. You got tired of and eventually felt a revulsion against things if you had to eat them often. This latter belief was supported by stories of people who through force of circumstances had been compelled, for instance, to live for two weeks on sardines and crackers and who, according to the stories, had sworn that so long as they lived they never would touch sardines again. The Southerners had it that nobody can eat a quail a day for thirty days.
There were subsidiary dietetic views. It was desirable to eat fruits and vegetables, including nuts and coarse grains. The less meat you ate the better for you. If you ate a good deal of it, you would develop rheumatism, hardening of the arteries, and high blood pressure, with a tendency to breakdown of the kidneys—in short, premature old age. An extreme variant had it that you would live more healthy, happily, and longer if you became a vegetarian.
Specifically it was believed, when our field studies began, that without vegetables in your diet you would develop scurvy. It was a"known fact" that sailors, miners, and explorers frequently died of scurvy ‘because they did not have vegetables and fruits.’ This was long before Vitamin C was publicized.”
Stefansson continued:
“A belief I was destined to find crucial in my Arctic work, making the difference between success and failure, life and death, was the view that man cannot live on meat alone. The few doctors and dietitians who thought you could were considered unorthodox if not charlatans. The arguments ranged from metaphysics to chemistry: Man was not intended to be carnivorous—you knew that from examining his teeth, his stomach, and the account of him in the Bible. As mentioned, he would get scurvy if he had no vegetables. The kidneys would be ruined by overwork. There would be protein poisoning and, in general hell to pay.”
“Not so long ago”? These beliefs still hold sway today, not only among physicians, dietitians, and nutritionists, but also among anthropologists seeking to explain human evolution. The assumption that human ancestors were vegetarians, and could not have lived on meat alone now gets supported by citing the brain’s supposed requirement for glucose, the existence of glycogen stores in the liver and muscles, and the production of amylase, the starch-digesting enzyme.
In 1918, after living with the Eskimos as an Eskimo for eleven years, Vihljalmur Stefansson returned to the U.S. and began giving lectures in which he reported that the Eskimo diet contained no vegetal foods, consisted only of meat and fat, most of the year; and that he and members of his expeditions, including Caucasians, Cape Verde Islanders with a strain of Negro blood, and South Sea Islanders, had lived on meat and water for years at a time.
Proponents of vegetarian diets, particularly John Harvey Kellogg, M.D., called Stefansson a liar, saying that humans can’t live without eating vegetal foods.
To prove his claim, Stefansson and consented to subject himself to scrutiny of a team of physicians while they ate a diet consisting entirely of meat and fat for one year straight. Karsten Anderson, a Danish man who had accompanied Stefansson on his third Arctic expedition, also consented to the study.
Anderson had several characteristics making him a suitable subject for the study. First, he had experience with the meat-and-water diet, so he would not suffer from the handicapping beliefs in the inadequacy of a meat-only diet, which can easily generate psychosomatic illness – a factor that plays a major role in many anecdotal reports of feeling unwell on diets restricting or lacking vegetal foods. Second, Anderson had at one point suffered from scurvy while on a mixed diet, and recovered from it on a meat-only diet.
Third, Anderson had for several years lived in Florida, working on his own, spending most days outdoors in sunlight, and eating a diet rich in vegetal foods. On this sunshine-supplemented mixed diet, Anderson suffered from frequent head colds, thinning hair, and, as Stefansson described it, “intestinal toxemia such as would ordinarily cause a doctor to look serious and pronounce: ‘You must go light on meat.’ or ‘I am afraid you'll have to cut out meat entirely.’"
During the year on the meat diet, Stefansson ate his meat well-done, and Anderson medium. They ate such foods as “steaks, chops, brains fried in bacon fat, boiled short-ribs, chicken, fish, liver and bacon.” According to Stefannson, Eskimos typically only ate the heads, briskets, ribs, pelvis and the marrow from the bones, and gave the organs, entrails, hams, shoulders, and tenderloin to their dogs. The men followed the Eskimo habit of eating fish bones and chewing rib ends.
After the year passed, the physicians subjected the men to a battery of tests to ascertain the “damage” done by going one full year without vegetal foods. They found ….. no damage at all. In fact, on the meat diet, Andersen had fewer colds, less hair loss, and a remission of symptoms of the intestinal microbial toxemia, and Stefansson lost ten pounds of fat. Stefansson felt optimistic and had an abundance of energy. Exercise tests showed that the men had an increase of physical stamina as the experiment progressed.
Chemists determined that the meat diet was very “low” in calcium, but no test performed on the men revealed any calcium deficiency, and the men looked healthier and felt better than they had on their previous mixed diets. The researchers hypothesized that though this lack of calcium had no effect over short one-year duration of the experiment, it might have severe effects over 10 or 20 years. To test this hypothesis, a secondary study was performed by Dr. Earnest A. Hooton, Professor of Physical Anthropology. Hooton examined the Peabody Museum collection of bones of Eskimos known to have died before European contact. Hooton found no evidence of calcium deficiency in those skeletons; on the contrary, those bones indicated that the Eskimos had adequate if not liberal calcium in their diet.
This study proved that man can live, even thrive, on a meat diet, for a lifetime. You know that neither chimp nor gorilla would survive in the niche exploited by Eskimos.
All these findings suggest that their previous mixed diet contained some factor(s) which caused illness. Removing plant foods removed the factor(s) and allowed these men to achieve a more natural condition, known as health. Perhaps they did not need to go so far, but again they proved a point: humans can maintain or even improve health without eating any plant food.
Meat your teeth
One of the most important issues in nutrition consists of its effects on dentition. So long as Eskimos lived on exclusively meat diets, they had no tooth decay. All meat-eating tribes maintain complete immunity to dental decay. In contrast, all tribes on mixed diets have some tooth decay, and the incidence of tooth decay increases in direct relationship to the amount of fermentable carbohydrate in the diet, a dose-response manner.
In the absence of dentistry and oral hygiene, in any species, reproductive success absolutely depends on a very high if not complete resistance to oral infections and dental decay. Chronic oral infection or significant tooth decay causes feeding disability, nutritional deficiency, metabolic disease, and reproductive failure.
In fact, we have good evidence that oral infection either causes infertility, or that oral infection and infertility have the same cause.
Bieniek and Riedel reported that among patients with subfertility and bacteriospermia, “It could be demonstrated that the bacterial spectrum of the intraoral samples was almost identical with the spermiograms.” [Bacterial foci in the teeth, oral cavity, and jaw--secondary effects (remote action) of bacterial colonies with respect to bacteriospermia and subfertility in males.]
Khader et al found that women with periodontal disease had a 4.28 times greater risk of preterm birth, only manageable with modern medical care. [Periodontal diseases and the risk of preterm birth and low birth weight: a meta-analysis.]
Xiong et al reviewed 25 studies of periodontal disease and pregnancy outcomes, and found that 18 of them found an association between periodontal disease and increased risk of adverse pregnancy outcome, including preterm low birthweight, low birthweight, preterm birth, birthweight by gestational age, miscarriage or pregnancy loss, and pre-eclampsia, with the highest odds ratio of 20. [Periodontal disease and adverse pregnancy outcomes: a systematic review.]
This evidence indicates that diets that promote tooth decay significantly impair fertility. This further drives home the point that oral infections and dental decay are maladaptive, as are any diets that promote oral infections and dental decay.
Hence, if certain level of intake of a class of foods promotes tooth decay in a given species, we can conclude that the species has not adapted to consumption of that class of foods beyond the level that clearly increases the occurrence of tooth decay.
Let me put it another way.
If human ancestors ate a diet rich in fermentable carbohydrates, which in modern humans promotes dental/oral infections or inflammation, those who had a high resistance to oral infections and caries produced by acidogenic bacteria while eating a diet high in fermentable carbohydrates would have had more children than those who had a low resistance. Those people who succumbed to tooth decay and oral infections would have had fewer offspring, and those who had high resistance to caries despite consumption of fermentable carbohydrate would have had more offspring. Over the millennia, given a situation in which people had no choice but to eat large volumes of fermentable carbohydrate (tubers, grains, etc.), the oral disease and resultant suboptimal fertility imposed by such diets would have by natural selection eliminated from the species all or virtually all humans having high susceptibility to dental decay when fed fermentable carbohydrate.
If this had happened, modern humans would maintain excellent dental health on a diet high in fermentable carbohydrates.
Since this is exactly the opposite of our current situation, we can conclude that our ancestors did not eat much of foods containing fermentable carbohydrates. The fact that we have no adequate defense against the tooth decay produced by diets high in fermentable carbohydrates tells us that our ancestors’ diets most likely contained little or no sugar or starch most of the time. Yes, they may have eaten honey or tubers on occasion, but these most likely were not put in the mouth very often or in very large amounts relative to non-fermentable foods.
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