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Evolution of the Human Diet

It is often argued by meat-eating humans in defence of their diet that modern man is evolved from pre-historic men that ate meat as a major component of their diet. Since our evolutionary ancestors ate meat, we must be biologically adapted to eat meat and therefore it is only natural for us to kill animals and eat meat.

Below you will read 2 articles that examine the case for and against the theory that humans are adapted to eat meat:

Barking Up the Wrong Tree?

However, by using a study of the evolution of man for deciding on one's own diet is missing the point somewhat. Even if we accept that pre-historic man did eat raw meat as a major part of its diet, it does not justify why we should. That justification ignores the fact that pre-historic man lived in the wild as a hunter; he didn't cage, enslave or mistreat the animals that he ate. The animals he ate were the weakest and easiest caught of their species. Ancient man was part of the natural selection process.

Neither did pre-historic man capture animals, pump them so full of unnatural chemicals that it poisoned the animals and destroyed the Earth's waterways. He didn't artificially inseminate animals and maintain them in this burdensome state so that he could drink their milk. He didn't keep animals in such vast numbers that they were choking the entire world and causing global warming.

Pre-historic man also wasn't aware of nutritional facts and the damage to his health that dairy and meat products can do. Perhaps if he was aware of all of this, he wouldn't have eaten any meat. Who knows? What is certain is that he didn't have the dietary choices that modern man has. We certainly don't need to eat meat for any nutritional benefit, the range of healthier alternative foods available to us now is so enormous.

We have evolved from pre-historic man, just as we have evolved from medieval man. Mankind has a sordid history full of mistreatment of those that it came into contact with - different races, different religions, homosexuals, women, children, animals; nearly always the weak, nearly always those that needed our help and support the most. Surely it's time our own ethics dictated our diets, not some debatable evolutionary theory based on pre-historic man. With that in mind, we present you 2 articles that examine whether humans are evolved to eat meat ...

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Are We Natural Carnivores?

The ever-popular beef burger remains popular amongst meat eaters - photo courtesy of Johnny Greig:

Several times recently I have heard on the media people saying "I know we are designed to eat meat but ..." or "I know we are natural carnivores but ..." and perhaps make a plea for a more compassionate treatment of animals. What shocks me is that these people are educated, well read and must be reflecting what our intellectual leaders accept as fact.

But looking at the facts, we can find no reason to suppose that the human digestive system was designed for the eating of flesh and we can point to the many facts that point to the human digestive system being designed for the assimilation of plant foods. So the statement "we are naturally carnivores" merely means "I and the majority of people I know regularly eat meat and think that this is the basis of a good meal". Certainly most humans are able to digest flesh foods and gain nourishment from them, but carnivorous dogs are able to adapt and thrive on a plant based diet, so this only proves that digestive systems can adapt to different diets.

The 19th Century scientist, T.H. Huxley, who was a staunch defender of Darwin's theories against the denunciations of Church leaders, made a special study of the physiology of carnivores compared to creatures with other diets and prepared a list showing that carnivores have completely different systems from humans.

I well remember being in a fishing village where I saw a fisherman throw a fish to an eagerly waiting cat. The cat caught it deftly although the fish was comparatively large, swallowed it, apparently whole and walked away, contented and happy. It reminded me of an occasion long before, when I had eaten a part of a small fish with the bones still in it and suffered pain for quite a while afterwards. I am told that carnivores have in their stomach hydrochloric acid 10 times the concentration that humans have. This means they break down flesh (and even fish bones) much more quickly than we can. Another important difference is that they have comparatively shorter intestines than humans have. As a result carnivores will assimilate flesh more quickly and efficiently, and also eliminate it more quickly.

I have been told that pork is the hardest flesh food to digest and can lie in the stomach for up to 4 hours before it is completely digested,. Yet many cultures eat pork although Moses, in his wisdom, banned it for his followers. What an ordeal eating meat must be for the human digestion! Other flesh foods also take longer for our stomachs to break down than plant foods do. Dead flesh begins to putrefy in a matter of hours after the death of the animal, which is why such care has to be taken to keep meat refrigerated. The long time that it takes for flesh to be digested by humans can only lead to a danger of putrefaction occurring in our digestive systems, especially during the long time spent in the large intestine. It is no coincidence that vegetarians are 10 times less likely to suffer from cancer of the bowel than meat eaters.

Carnivores kill their prey and usually eat it whilst still warm. Human hunters carry their prey home and cook it with tasty herbs before they will eat it. The 19th Century author, Charles Lamb wrote a famous essay in which he suggested that roast pork had first been discovered when a pig had accidentally been burnt in a fire. There may be a germ of truth in the notion. Humans probably used fire at the entrance of caves to keep out wild animals. Maybe one day they discovered an animal burnt on the fire and tasted it. Maybe this happened at a time when plant foods were scarce. We can only conjecture.

What is commonly accepted is that pre-historic humans were 'hunter-gatherers'. Whilst the women of the tribe gathered fruits, plants and herbs, the men are supposed to have gathered together to track and slay an animal for an occasional feast. This viewpoint has been put forward by male, meat-eating anthropologists who suggested that the cunning needed to hunt the animal helped develop intelligence and social skills.

The view of Barbara Nolke, a female vegetarian anthropologist, is that the women of the tribe, who had to identify and know where to find the various plants and herbs and study their use in nutrition and healing, were the ones with the more developed intelligence. She also suggests that humans were more likely to have taken to meat by scavenging the corpses left by the carnivores who would be more efficient at hunting. Even so, there seems to be no evidence of animals being eaten uncooked, not even among cannibals and we cannot be classed as 'natural carnivores' if we had to wait for the discovery of fire before we could eat meat.

Turning to our digestive system, this starts in the mouth. Remember that the cat swallowed the fish without chewing it. It caught the fish with its jagged, interlocking teeth that hold the prey firm. Human teeth in the same back position are flat molars (that means grinders) used for the grinding of grains. Our jaws can move in a backward and forward motion and also from side to side, ideal for grinding. At the same time, our saliva produces enzymes to break down starches. "But surely we have canine teeth?" someone invariably asks. Look at a cat or a dog's canine teeth and you will see that they project down further than the others, like those of an imaginary blood-sucking vampire. So our canines cannot have any use for attacking prey and our jaws do not project forward from the face as they do with cats and dogs. Our front teeth are well adapted for biting fruit and cutting up vegetables.

As previously mentioned our gastric juices contain less hydrochloric acid than that of carnivores, but are well adapted for the digestion of starches. Our longer colon is suited for a slow process of digestion, extracting a great variety of essential nutrients. The study of human nutrition has advanced greatly in recent years and continues to discover the importance of minute quantities of certain minerals and vitamins, their interconnectedness and the role of various enzymes in the digestive process. Plant foods show themselves to be well adapted for providing the wide range of minerals and vitamins that our bodies require, unless perhaps when they are over refined or overcooked. We should be more conscious of the importance of sound nutrition, rather than the crude notion of filling the hunger gap with a steak or sausage.

By the comparative study of populations having different diets, modern nutritionists have pointed out the benefits of the 'Mediterranean diet' which is very low in animal fats, but high in vegetable oils, relying on pulses and grains (such as pasta) and consuming many fruits and vegetables. A comparison of people in the South of Italy where plant foods abound, with the unfortunate Finns who have to depend more on animal products and fats, show that Finns are massively prone to heart disease. Those living in the frozen Arctic wastes, such as the Inuit or Eskimos, have to rely exclusively on animals for their food, die in their 40s and suffer from osteoporosis (weak bones due to a shortage of calcium). Vegans, contrary to popular expectation, have a plentiful source of calcium in plant foods, providing they eat a varied diet, and are less prone to osteoporosis.

Vegans do not have to depend on cooking. Some foods which vegans eat may be digested after being cooked, but a surprising quantity and diversity of foods can be eaten raw and are probably more nutritious in their raw and fresh state. Fruits and nuts can obviously be eaten raw, as too can the vegetables we eat in salads, including grated carrots and beetroot, and also other vegetables not normally included in salads. Onions and garlic can be eaten raw, but maybe you should experiment with the latter only when you will be alone for a while afterwards. Grains can be flaked and eaten raw as in muesli. Pulses in their raw state would appear to be a problem but many of them may become easily digestible if you first allow them to sprout (as in Chinese mung bean sprouts). They will sprout after being soaked and kept moist and warm for a few days. Peas and lentils sprout readily and are surprisingly sweet.

Our imagining ourselves to be carnivores may spring from our idea that carnivores are the most successful animal group; that the lion is the 'King of the Jungle'. This is far from the case. Deer with their antlers and swift movements can fend off an attacking lion or tiger. I have seen a cat flee from a solitary attacking bird. Herbivores are by far more numerous and can therefore arguably be considered as far more successful, which is just as well for the carnivores who could not exist without the herbivores they feed on.

Carnivores attack a herd of grazing herbivores and only catch the slowest and weakest. This action results in culling the weaker members of the herd, leaving the fitter ones to breed and maintain a higher level of fitness in the herd. The role of carnivores, far from being some dominant species, is that of one dependent on and subservient to other animals - playing a useful role but not supreme.

Neither, of course, can humans be classed as 'natural herbivores' for again these have quite different digestive systems, which include multiple stomachs, as with cattle and sheep, that can efficiently digest coarse grasses. Donkeys even eat thistles with great delight, but I would not recommend them as a suitable diet for humans. Ruminants first swallow their food into one stomach, then later sit calmly and chew it again for a second digestive process. I am sure that some humans would like to eat their food twice over but unfortunately we are not adapted for that.

Some people claim that we should be classed as omnivores, because we can subsist on a wide variety of foods. This suggestion could lead us into the false notion that we could live by eating just the stems of grasses as herbivores can, I doubt whether anyone would agree with that, although we can of course digest the grains of grasses, such as oats, wheat, etc. Since certain herbs and berries are highly poisonous to humans, the classification of omnivore would appear to have a limit somewhere.

However, there is a group of animals that we closely resemble and that is the primates or apes. It is said that we share >99% of our genes with chimpanzees, and it would be difficult to get closer than that. Chimpanzees, like many apes, rely mainly on fruit and green shoots for their nutrition. Most apes have been classified as frugivorous, which means eaters of fruits and nuts, and they also eat some vegetation. Japanese soldiers, who had to survive in the jungle, watched what the apes ate and did the same, and they survived because of that.

Those who watch nature films may point out that they have seen apes scooping out ants and eating them (would you fancy that?) and even hunting other apes in order to eat them. Perhaps these are on the way to developing the bad habits we can find in some humans, but, as hopefully with humans, we can assume that this is not connected with nutritional needs. Many of the great apes, such as gorillas, are also frugivorous. They are very strong and powerful but have a gentle and caring disposition. With their superior intelligence and great strength, these great apes can surely claim the title of 'King of the Jungle' and be worthy of our admiration and emulation. The scavenging lions and tigers can be relegated to their roles of refuse collectors.

One thing is clear in my mind: we are not 'natural carnivores' and until we understand this, our bodies and our minds will not find true health. Nor will we attain the civilised standard that we require to merit our position at the top of the primates league, and our planet will not attain the order and harmony necessary for it to thrive and remain functional. For what we eat not only affects our bodies and minds, but, owing to the vast proliferation of humans on the globe, it has a great impact on the whole of the earth - but that would lead to a whole new chapter to explain.

Written by Harry Mather, Vegan ViewsOpens in a new window

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Are Humans Natural Frugivores?

The frugivores (gorillas, chimpanzees and other primates) have intestinal tracts 12 times the length of the body, clawless hands and alkaline urine and saliva. Their diet is mostly vegetarian, occasionally supplemented with carrion and insects, etc.

Oranges are a great source of vitamin C - photo courtesy of Johnny Greig:

Flesh-eating animals lap water with their tongue, whereas vegetarian animals imbibe liquids by a suction process. Humans are classified as primates and are thus frugivores, possessing a set of completely herbivorous teeth. Proponents of the theory that humans should be classified as omnivores note that human beings do in fact possess a modified form of canine teeth. However, these so-called canine teeth are much more prominent in animals that traditionally never eat flesh, such as apes, camels, and the male musk deer.

It must also be noted that the shape, length and hardness of these so-called canine teeth can hardly be compared to those of true carnivorous animals. A principle factor in determining the hardness of teeth is the phosphate of magnesia content. Human teeth usually contain 1.5% phosphate of magnesia, whereas the teeth of carnivores are composed of nearly 5%. It is for this reason they are able to break through the bones of their prey, and reach the nutritious marrow.

Zoologist Desmond Morris made a case for vegetarianism in his 1967 book, The Naked Ape: "It could be argued that, since our primate ancestors had to make do without a major meat component in their diets we should be able to do the same. We were driven to become flesh eaters only by environmental circumstances, and now that we have the environment under control with elaborately cultivated crops at our disposal, we might be expected to return to our ancient feeding patterns."

In The Human Story, edited by Marie-Louise Makris (1985), we read: "... recent studies of their teeth reveal that the Australopithecines did not eat meat as a regular part of their diet, and were mainly peaceful vegetarians, rather like chimps or gorillas. The popular image of the murderous ape is now as extinct as the Australopithecines themselves."

Dr. Gordon Latto notes that carnivorous and omnivorous animals can only move their jaws up and down, and that omnivores "have a blunt tooth, a sharp tooth, a blunt tooth, a sharp tooth - showing that they were destined to deal both with flesh foods from the animal kingdom and foods from the vegetable kingdom ..."

"Carnivorous and omnivorous mammals cannot perspire, except at the extremity of the limbs and the tip of the nose; man perspires all over the body. Finally, our instincts; the carnivorous mammal (which first of all has claws and canine teeth) is capable of tearing flesh asunder, whereas man only partakes of flesh foods after they have been camouflaged by cooking and by condiments".

"Man instinctively is not carnivorous," explains Dr. Latto. "...he takes the flesh food after somebody else has killed it, and after it has been cooked and camouflaged with certain condiments. Whereas to pick an apple off a tree or eat some grain or a carrot is a natural thing to do; people enjoy doing it; they don't feel disturbed by it. But to see these animals being slaughtered does affect people; it offends them. Even the toughest of people are affected by the sights in the slaughterhouse".

"I remember taking some medical students into a slaughterhouse. They were about as hardened people as you could meet. After seeing the animals slaughtered that day in the slaughterhouse, not one of them could eat meat that evening" (see our vegan advocate article for more on effective advocacy strategies).

Author R.H. Weldon writes in No Animal Food: "The gorge of a cat, for instance, will rise at the smell of a mouse or a piece of raw flesh, but not at the aroma of fruit. If a man can take delight in pouncing upon a bird, tear its still living body apart with his teeth, sucking the warm blood, one might infer that nature had provided him with a carnivorous instinct, but the very thought of doing such a thing makes him shudder. On the other hand, a bunch of luscious grapes makes his mouth water, and even in the absence of hunger, he will eat fruit to gratify taste".

As far back as 1961, the Journal of the American Medical Association reported that: "A vegetarian diet can prevent 97% of our coronary occlusions." More recently, William S. Collens and Gerald B. Dobkens concluded: "Examination of the dental structure of modern man reveals that he possesses all the features of a strictly herbivorous animal. While designed to subsist on vegetarian foods, he has perverted his dietary habits to accept food of the carnivore. It is postulated that man cannot handle carnivorous foods like the carnivore. Herein may lie the basis for the high incidence of arteriosclerotic disease".

Keith Akers in A Vegetarian Sourcebook (1983), responds to the argument that killing animals for food is natural: "The main problem with this argument is that it does not justify the practice of meat-eating or animal husbandry as we know it today; it justifies hunting. The distinction between hunting and animal husbandry probably seems rather fine to the man in the street, or even to your typical rule-utilitarian moral philosopher. The distinction, however, is obvious to an ecologist. If one defends killing on the grounds that it occurs in nature, then one is defending the practice as it occurs in nature".

"When one species of animal preys on another in nature, it only preys on a very small proportion of the total species population. Obviously, the predator species relies on its prey for its continued survival. Therefore, to wipe the prey species out through overhunting would be fatal. In practice, members of such predator species rely on such strategies as territoriality to restrict overhunting and to insure the continued existence of its food supply".

"Moreover, only the weakest members of the prey species are the predator's victims: the feeble, the sick, the lame, or the young accidentally separated from the fold. The life of the typical zebra is usually placid, even in lion country; this kind of violence is the exception in nature, not the rule".

"As it exists in the wild, hunting is the preying upon isolated members of an animal herd. Animal husbandry is the nearly complete annihilation of an animal herd. In nature, this kind of slaughter does not exist. The philosopher is free to argue that there is no moral difference between hunting and slaughter, but he cannot invoke nature as a defence of this idea".

"Why are hunters, not butchers, most frequently taken to task by the larger community for their killing of animals? Hunters usually react to such criticism by replying that if hunting is wrong, then meat-hunting must be wrong as well. The hunter is certainly right on 1 point - the larger community is hypocritical to object to hunting when it consumes the flesh of domesticated animals. If any form of meat-eating is justified, it would be meat from a hunted animal."

In his 1975 book, Animal Liberation, Australian philosopher Peter Singer writes: "Killing an animal is in itself a troubling act. It has been said that if we had to kill our own meat we would all be vegetarians. There may be exceptions to that general rule, but it is true that most people prefer not to inquire into the killing of the animals they eat".

"Very few people ever visit a slaughterhouse; and films of slaughterhouse operations are rarely shown on television. Yet those who, by their purchases, require animals to be killed have no right to be shielded from this or any other aspect of the production of the meat they buy".

"If it is distasteful for humans to think about, what can it be like for the animals to experience it?"

Peter Singer concludes in Animal Liberation that "by ceasing to rear and kill animals for food, we can make extra food available for humans that, properly distributed, would eliminate starvation and malnutrition from this planet. Animal Liberation is Human Liberation, too".

Finally, even if humans really are omnivores as some claim (and this claim is subject to dispute), I would refer these people to Dr. Milton Mills or the Physicians Committee for Responsible MedicineOpens in a new window, which advocates a vegan diet, and an end to vivisection, etc. For the latest on whether humans are frugivorous or omnivorous, my friend Mareechi Duvvuuri who once studied sports medicine, pointed out that the diet of natural omnivores is mostly (85%) plant food.

Written by Vasu MurtiOpens in a new window

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