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Humans have always eaten meat… right? No, actually we haven’t. (Just because we assume that humans have always eaten meat doesn’t make it true.) The best evidence for what we’re optimized to eat is our digestive system, so let’s examine it.

Teeth
The teeth of a carnivore are long and pointed, for tearing raw flesh. Herbivores have flat teeth and flat back molars to grind their food. Carnivores do not have flat back molars at all.  Some herbivores do have small, what we call “canine” teeth for biting into tough plants (like apples) but these are nothing compared to the size and shape of a carnivore’s teeth. True omnivores’ teeth are most similar to carnivore teeth.

Carnivores:

True Omnivores* (Bears eat fish and berries, Rats scavenge nearly everything from grains to veggies to meat):

Herbivores:

Which look most like yours?

*By “true omnivore” I mean animals that naturally eat both plants and animals. For example, cats eat vegetables (in their commercial cat food, or maybe it’s handed to them under the table) but cats are not true omnivores, they are carnivores. In the wild, cats would eat birds and rodents, not leaves and berries.

Jaws
The jaws of carnivores move up and down, but not side to side. The jaw motion of an omnivore is similar. They don’t chew. This is because carnivores tear off meat and swallow it whole. An herbivore’s jaw moves both up and down and side to side for grinding vegetation. Check your jaw and see what it does.

Saliva
A carnivore or omnivore has small salivary glands in their mouth and their saliva does not contain digestive enzymes. Herbivores’ saliva is alkaline, containing carbohydrate digestive enzymes to pre-digest plant food. Herbivores also have large, developed salivary glands in their mouth. Human saliva is alkaline and contains digestive enzymes. And our salivary glands are large.

Tongue
From an article by John A. McDougall, M.D.:

“Cats are obligate carnivores – they must live on a diet primarily of meat – and their taste buds reflect this by having abandoned the tongue sensors that respond to sweet-tasting carbohydrates.  Dogs are omnivores – they have retained both kinds of taste buds – those enjoying carbohydrates and amino acids.  Humans tongues respond pleasurably to sweet (carbohydrates), but have lost the taste for amino acids, placing us undeniably in the category of herbivores (plant eaters).”

Additionally, herbivores drink by sucking water up into their mouths as opposed to lapping it up with their tongue which all carnivores do.

Intestines
A carnivore’s or omnivore’s small intestine is 3 to 6 times the length of its trunk. This is designed for rapid elimination of food that rots quickly. An herbivore’s small intestine is 10 to 12 times the length of its trunk, and winds itself back and forth in random directions. This is designed for keeping food in it for long enough periods of time to extract all the valuable nutrients and minerals before the food enters the large intestine.

A carnivore’s or omnivore’s large intestine is relatively short and simple, like a pipe. This passage is also relatively smooth and runs fairly straight so that fatty wastes high in cholesterol can easily slide out before they start to putrefy. (This is why it’s impossible for carnivores to get cancer or heart disease from high cholesterol and clogged arteries.) An herbivore’s large intestine, or colon, is puckered and pouched, an apparatus that runs in three directions (ascending, traversing and descending), designed to hold wastes that originally were foods high in water content. This is so that the fluids can be extracted from these wastes, now that all the useful nutrients and minerals have been extracted. Substances high in fat and cholesterol that have been putrefying for hours during their long stay in the small intestine tend to get stuck in the pockets that line the large intestine. (Vegetarians have lower rates of colon cancer.)

Care to guess which type of intestines we have? (Hint: Human small intestines are about 10 times our torso length and our large intestines are puckered.)

Stomach
A carnivore can eat rotting, bacteria-ridden flesh completely raw without getting sick. They have stomach acids that kill the bad stuff and allow them to digest the rest without puking their guts up. Their stomach secretes powerful digestive enzymes with about 10 times the amount of hydrochloric acid than that of a human or herbivore. The pHis less than or equal to 1 with food in the stomach, for a carnivore or omnivore. For herbivores and humans, the pH ranges from 4 to 5 with food in the stomach. Hence, man must cook his meats. Ever try to eat road kill? Or a freshly dead chicken, completely raw? Give it a shot and let me know how it works out for you. E. Coli bacteria, salmonella, campylobacter, trichina worms, parasites, or other pathogens would not survive in the stomach of a lion.

Liver
Animal flesh is composed of the most highly complex type of protein and requires vast amounts of uric acid to process. Uric acid is released into the system in amounts necessary to break proteins down into amino acids. Uric acid is a toxic substance responsible for the aging process and must be flushed out and dealt with. That is one of the jobs of the liver. In relative terms, a carnivore’s liver is a tool designed with the capacity to eliminate ten times as much uric acid as the liver of man or other plant eaters.

Our anatomy and digestive system clearly show that we must have evolved for millions of years living on fruits, nuts, grains, and vegetables.

Still skeptical?

Physical features
Carnivores and omnivores have physical characteristics which enable them to chase, trap, and kill. Speed, sharp teeth, and claws are tools meant to hunt, kill, and rend tough flesh. Examine your hand, fingers and fingernails. Is this an apparatus properly designed for catching, trapping, killing, and ripping apart cattle, hogs, chicken and fish? (How do they work for picking fruit from trees or harvesting vegetables?) Meat eaters have the speed and reflexes to catch prey. You do not. Try to catch an animal that doesn’t want to be caught (without tools or weapons) and you’ll get an idea of what type of hunter we naturally are.

Sweat
Meat-eating animals that hunt in the cool of the night and sleep during the day when it is hot do not need sweat glands to cool their bodies; they therefore do not perspire through their skin, but rather they sweat through their tongues. On the other hand, vegetarian animals, such as cows, horses, zebras, deer, etc., spend much of their time in the sun gathering their food, and they freely perspire through their skin to cool their bodies.

Sleep
Carnivores sleep the most, herbivores the least, and omnivores in the middle. Guess which group our own sleep correlates with.

Here are some charts from an article in Nature. They have stuck us (and other primates) in the omnivore group (because that’s what everyone assumes we are) but notice that we’re at the extreme end of that chart, with nearly every other single omnivore sleeping more than we do. However, we fit nicely in the herbivore chart. A prominent dot for humans is added to the herbivore chart to show how we fit in at eight hours a night.

Carnivores (most sleep):

Omnivores:

Herbivores (least sleep):

Instincts
It is obvious that our natural instincts are non-carnivorous. Natural meat eaters find the smell of blood and dead animals attractive. How do you think they smell?

Carnivores kill without sympathy or remorse. Humans (obviously) do not.

One scientist explains it this way: “A cat will salivate with hungry desire at the smell of a piece of raw flesh but not at all at the smell of fruit. If man could delight in pouncing upon a bird, tear its still-living limbs apart with his teeth, and suck the warm blood, one might conclude that nature provided him with meat-eating instinct. On the other hand, a bunch of luscious grapes makes his mouth water, and even in the absence of hunger he will eat fruit because it tastes so good.”

Unlike other animals, humans can act outside of instinct. Other animals are programmed to know what food is. We are not. For us, it’s learned behavior. Or, in the beginning, guessed behavior. We can make choices about what we eat even if that’s contrary to good health (as millions prove every day when they eat at McDonald’s). When our ancestors ate meat, they were being human and making choices, rather than acting on instinct. Think about it: Do you really believe that cavemen were true experts about nutrition? If so, what other major decisions about your life would you like to put in the hands of a caveman?

Health
In general, plant-eating creatures have the longest lifespans. Elephants, horses, and chimpanzees are at the top of the list while lions, tigers, and wolves are about half that. Humans’ lifespans are even longer than the elephants (even before modern medicine), providing more evidence that we’re in the plant-eating camp.

Science and medical evidence overwhelmingly shows that the more meat we eat, the sicker we get - heart disease, cancer, diabetes, osteoporosis, and every other major degenerative disease. If eating meat were so natural, it wouldn’t destroy our health.

Dean Ornish, M.D. was the first person to prove that heart disease can be reversed, and he did so by feeding his patients a vegetarian diet. John McDougall, M.D. has also written extensively about how animal foods cause disease, and how people can regain their health by eating vegan instead. The esteemed T. Colin Campbell oversaw the most massive study of the relationship between diet and disease, the China Study, which the New York Times called “the grand prix of epidemiology.” His conclusions are the same as the other experts: we’re not designed to eat animal foods, because we get sick when we do.

The fact that health can be regained by laying off meat and dairy is powerful evidence that we shouldn’t have been eating those foods in the first place.

By now, the meat-eating reader already has objections.
Let me try to address some of these.

Objection 1: We’re capable of eating meat, therefore we’re omnivores.
Cats are also capable of eating both plants and meat.  In fact, some people feed their cats a purely vegan diet.  But cats are not omnivores, they are carnivores (as previously explained). True omnivores are not just capable of eating both plants and animals, but their bodies are optimized for it. Just because we can digest meat doesn’t mean that we’re supposed to. We can digest cardboard, but that doesn’t mean that we should.

Objection 2: Vitamin B12 is only obtained from meat, dairy, and eggs.
B12 isn’t made by animals, it’s made by bacteria. It’s found where things are unclean (and rotting flesh is dirty).  This easily explains why historically it’s been easy to get B12, because until recently we didn’t live in a sanitized environment. Pull a carrot out of the ground and don’t wash it properly, and there’s almost certainly some B12 there. Vegans should take a B12 supplement, not because veganism is unnatural, but because the modern diet is too clean to contain reliable natural sources of dirty B12.

Incidentally, our need for B12 is tiny: 3 micograms a day (not milligrams, micrograms). The amount of B12 you need for your entire life is smaller than four grains of rice.

Objection 3: Other primates eat meat.
Hardly. A chimp’s diet is 95-99% plant foods, and the non-plant food isn’t meat, it’s termites. We also have to remember that primates are intelligent and can make choices outside of instinct, just like humans do, so the tiny amount of non-vegetarian food they might eat could simply be due to choice, not instinct.

Others? Leave a comment.

____________________
Breakfast: An awesome smoothie! Banana, pear, kale, and hemp milk.

Lunch: Leftover vegan pizza, blueberries, and an orange

Dinner: Mexican food! Enchilada, vegan beef taquito, soy chorizo taco, and vegan queso (I add salsa to this recipe)

This entry was posted on Wednesday, June 9th, 2010 at 12:32 am and is filed under Miscellaneous. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.