Humans Are Naturally Herbivores


I’m making separate posts on individual issues related to Veganism so that anyone who wants a handy reference guide to each issue won’t have to go through my entire link list to find it. The links included in each individual post may not be updated regularly so the Master List will be the only place to find complete updates. These posts will be comprehensive enough to cover most or all questions related to each issue, however.

Saying that exploiting animals for food or other reasons is “natural”, and therefore it’s beneficial because we’ve been doing it for all of recorded history and that makes it morally justifiable is irrational, since many things we consider detrimental to humans regarding moral matters occur in nature (either perpetrated by humans on other humans or by nonhumans on other nonhumans).

We have been enslaving, raping, torturing and murdering humans for all of recorded history and most people don’t feel that those things are morally justifiable, even though they can be described as completely natural. If it’s unnecessary to do something in the present and it harms a sentient being, then how does pointing to the fact that we did it in the past or that nonhumans do it make it morally justifiable?

In other words, the term “natural” has no bearing whatsoever on the subject of morality.

However, there is a real concept that relates to the term “natural” regarding our diet. That is what we call “nutritional science” or “dietetics.”

According to biology, a species’ natural diet is made up of individual foods that that species can metabolize without those foods causing a member of that species to begin or continue to develop chronic disease. That is how science determines “natural” diets when we talk about all nonhuman animals.

Thus, if we take a cow, for instance, and begin to feed animal flesh to her, we would see her begin to develop chronic disease (most notably atherosclerosis). That is how we know that the cow’s “natural diet” is herbivorous. We know the cow is what we call “a herbivore.” Physiology determines what dietary classification an animal is, not behavior. To illustrate this, we can do a thought experiment. Let’s say we take a pile of animal flesh and grind it up and mix it into a ground-up pile of corn. Next to that, we put a pile of animal flesh, unground.

If we let a starving cow decide, they will usually eat the corn/flesh mixture rather than the pure flesh (and we actually do feed ground up chickens and cows to cattle every day on farms) until they’ve satisfied their hunger. However, just because the cow chose to eat a pile of corn and flesh mixed together, doesn’t mean they are an omnivore. Choosing to eat something didn’t change their dietary class from herbivore to omnivore because behavior doesn’t determine which dietary class you are, only physiology does. Once the cow has eaten all the flesh/corn mixture she needs to satisfy her hunger, the flesh will begin to cause her to develop chronic disease, just like any herbivore would.

Now, the thing is, humans undergo the same process of developing chronic disease that other herbivorous animals do.

The way it works is this. Let’s say you are a child that has never consumed animal substances. You eat a small bite of any animal substances, whether it be flesh, dairy or eggs. Doesn’t matter which of those substances, doesn’t matter how big.

Let’s call that *1 increment*

That 1 increment has what we’ll call “1 increment of animal proteins.” I focus on the proteins because the proteins are in every animal substance, cannot be separated out the way cholesterol or animal fats can be (proteins are the basic building block of all flesh, dairy, and eggs), they are as bad as cholesterol or animal fats and they are the one nutrient that is most misunderstood even by scientists. The cholesterol and animal fats are also horrible though and contribute to this phenomenon, obviously.

When you consume 1 increment of animal proteins (those proteins being chronically toxic) they cause your body to begin to develop chronic disease of various kinds. The mechanisms for this toxicity are actually caused by the ratio of inessential amino acids in all animal substances.

When you consume the second increment of animal proteins, your body continues to develop chronic disease. A third increment continues this, and so forth.

When you have consumed a sufficient quantity of increments of animal proteins, your body will start to show symptoms of one or more of the diseases in question. This is mitigated by a variety of circumstantial factors, including, but not limited to: genetic predispositions, environmental factors, amount and type of plant-based food consumed, etc. There is no telling from the beginning of consumption when and how these symptoms will first manifest, and which diseases the person in question will show symptoms from (unless tests have been performed to screen for genetic predispositions).

Now, when the person in question ceases consumption of animal substances, all other things being equal (no permanent damage to the immune system, or impending death, etc.) their body immediately begins to heal itself. This is why people who have horrible chronic diseases of all kinds, when they switch to a 100% whole-foods plants-only diet, immediately see huge improvements and have cured most or all of the diet-related disease they had.

You can actually perform an experiment to verify this. This is why people with cancerous tumors can omit animal proteins and eat a 100% whole-foods plants-only diet and watch their tumors shrink, and then re-introduce animal proteins and watch their tumors start to grow again. Many diabetes sufferers, when switching from the Standard American Diet to a 100% raw plant-based diet find that it’s dangerous to continue taking insulin after as little as 3 days.

Dr. T. Colin Campbell has done a 20-year study and correlated mountains of data just on this theory alone (not a hypothesis, a theory. 2 different things).

“But doesn’t ‘obligate herbivore’ mean ‘on pain of rapid death’?”

No. As I said, each increment causes a corresponding amount of disease. “Obligate herbivore” simply means that you begin to develop some amount of chronic disease from ANY amount of animal substances. It doesn’t speak to how much, in either instance.

In fact, if you eat animal substances but also plant substances, the beneficial nutrients in the plant substances mitigate the harmful effects of the animal proteins, animal fats, and cholesterol to an extent (plus any beneficial vitamins and minerals that happen to be present in the animal substances are some sort of factor). Remember, the human body has the ability to continually heal itself from harm that’s done to it – whether accidental or intentional. Our bodies do this by taking the nutrients that originate from plants and using them to drive certain actions -that our metabolisms are evolved to automatically engage in- that allow our bodies to regenerate damaged tissue. When you’re intentionally doing something harmful to yourself, it’s like you’re fighting a war inside your body, with the times you’re consuming the animal substances damaging your body and the times you’re not consuming them allowing your body to heal itself a bit.

People at this point are saying “but-but-but… we do get some nutrients from animal substances! How can this be, if they’re all toxic???”

The truth is that animal substances have nutrients that are not related to proteins, fats, and cholesterol in them, that the animals only gained from eating plant substances. So if you consume animal flesh or secretions you are getting recycled nutrients. These vitamins, minerals, etc. in the plants would normally be very healthy for you, and indeed are still mitigating the effects of the toxic animal proteins somewhat, but animal proteins, animal fats, and cholesterol are so toxic that there isn’t much that the good nutrients can do to overcome the bad effects of the animal proteins, fats, and cholesterol. Indeed, many animal substances cause the human body to block the absorption of the good nutrients in both animal substances and plant-based food.

You may ask “What about people who eat small quantities of animal substances….what about the Okinawans? Why are they so long-lived and healthy?”

You don’t need to do a study in Okinawa to extrapolate basic science to those people’s circumstances. They eat a diet low in animal substances. If someone in Okinawa ate no animal substances for their entire life, all other environmental factors being equal, they would be the healthiest person/people in Okinawa.

You might say “But my miscellaneous relative lived to the age of ___ and they ate tons of animal substances all of their lives. If animal substances are as toxic as you say they are, then how can that be?”

You have to remember one important thing here; the human body has the ability to heal. So if you eat animal substances for breakfast, along with some plant-based food, and then you don’t eat again for 3 or 4 hours, in the time you’re not eating, your body is trying to eliminate the toxic animal substances, and it’s using the plant-based food to try to do it. However, just as your body begins to get the upper hand, here you go eating more animal substances for lunch. Heal a bit, and then it’s dinner and more toxic proteins, fats, and cholesterol all over again. And this pattern repeats and repeats every day.

The best time for your body in this situation is while you sleep, but even with those longer periods of healing, if you eat flesh, dairy, and eggs every day, you can’t fight off the symptoms of disease for very long. It’s like fighting a war against your own body by continuously, slowly poisoning yourself little by little. Totally ridiculous. Also, there is the fact that different people do have different genetic propensities for different disease. However, most genetic predispositions for disease are like loaded guns,  in that they aren’t a foregone conclusion, but need an environmental trigger to activate them or they won’t do anything in most cases.

Also, the animal proteins and animal fats themselves can be used by the body to build its tissues and fuel its processes, however, since they are inferior to amino acids and fats from plants, the resultant body you build is just waiting to fail. The fact that our bodies are supposed to build our own proteins from amino acids in plants rather than the much more taxing work of breaking down the proteins that were already built by nonhumans and then using those aminos to build our proteins is one of the mechanisms that causes chronic disease in humans.

That’s why there are so many athletes who consume certain amounts of animal substances, and exercise and other environmental factors keep them muscular, but they either die early or have long-term chronic disease in their final years. Merely being “in good shape” when you’re younger does not mean your diet won’t eventually catch up to you. Older non-Vegans may sometimes seem healthy, but the stats belie that idea. I mean, just look at the booming pharmaceutical business. Most older people in developed nations are simply riddled with chronic disease. Then look at the percentage of Vegans with chronic disease.

Therefore, when we look at humans, and we see that the optimal diet for humans is fruits, vegetables and nuts (and arguably legumes and seeds can be added to that) and that any addition of animal substances like flesh, dairy or eggs causes chronic disease to begin or continue to develop , we can see that our natural diet is herbivorous also. This means that we are what we call an herbivore, which is a word that means not just browsers and grazers, but any being whose optimal diet includes only plant substances and no animal substances.

There are many different sub-classes of the main class called herbivores.

One sub-class is folivores, whose optimal diet is leaves (like koalas).
One is granivores, whose optimal diet is seeds (like mice and some birds).
There is a class called nectarivores, whose optimal diet is nectar (like the honey possum, and some bats, birds, and insects).
Palynivores optimal diet is pollen (like bees).
Mucivores drink plant fluids, like sap (aphids are in this class, among others)
Xylophages have an optimal diet of wood (like termites).

If you look at the chart below, you’ll see that there is a sub-class of herbivorous animals called “frugivores.” These are beings like gorillas, orangutans, chimpanzees, bonobos, and humans, whose optimal diet is made up mostly of fruits, vegetables, and nuts.

Obligate Comparison 01


Side note: just because we see miscellaneous videos of individual examples of some of these primates consuming termites, or even killing and eating monkeys does not mean they are omnivorous and that their optimal diet contains these things. Many of these behaviors are related to choice rather than necessity and I suspect that the animal proteins consumed because of this affect them the same way they do us.

If you compare the anatomy of carnivores, “omnivores” and herbivores across a wide spectrum, you’ll see that in regards to every physiological adaptation that we have, when compared to the same types of adaptations in many different nonhuman species in all three dietary classes, we skew towards herbivores and away from omnivores in all cases. There is no instance where there is a significant adaptation that can be proven to relate us to omnivores, where it does not relate us more closely to herbivores.

This is because we are physiologically herbivores.

The truth is that before we came down from the trees, we were frugivores, and in all the many millennia that we’ve been consuming animal substances, our digestive systems have not adapted one bit to allow us to metabolize those substances better than we did back then. We developed chronic disease from them back then, and we do so now.

Right now you may be asking “If all this is true, then why does almost every scientist call humans omnivores?”

It’s because, to put it simply, most scientists use the term “omnivore” wrong.

Think about it; when we use the term “herbivore” in strictly nonhuman contexts, we are talking about beings who can only be optimally healthy if their diet does not include any animal substances, but only plant substances. I mean, if a horse or a giraffe accidentally eats some insects along with the plants they browse and graze, we don’t call them omnivores, right? Of course not!

Similarly, when we use the word “omnivore” strictly in nonhuman contexts, we are talking about beings who can be optimally healthy by eating either animal substances or plant substances, or both. It’s not because they choose to eat both, it’s because they are biologically adapted to eat both and not develop chronic disease from doing so.

However, the minute we start talking about humans, most scientists change their tune! They claim “humans are omnivores because we eat both animal substances and plant substances’.”

Think about that for a second. With nonhumans, they eat what is optimally healthy for them, and we use their physiology to determine whether they are herbivores, “omnivores,” or carnivores. But when it comes to humans, we choose to eat both animal substances and plant substances, and animal substances always cause us to develop chronic disease. And yet, we call humans “omnivores” because we choose to eat those things! Talk about bias!

You may be asking why this is relevant to the moral argument for Veganism. I believe it’s relevant because for one thing: it’s the truth, and nothing good ever comes of misrepresenting the truth. But above and beyond all that, I want the world to be a place where the truth about exploiting nonhuman animals is made perfectly clear. And the truth is that there is no aspect of humans intentionally exploiting sentient beings that is more positive than negative. Indeed, in almost all cases, exploiting nonhuman animals has no real upside at all. Which means that intentionally exploiting animals will never help our situation. It can only harm us, as well as the nonhumans and everything on the planet.

It’s just the way it is y’all. We’ve got to deal with it.

Sources for the info presented in this post:

“Humans are naturally plant-eaters: according to the best evidence: our bodies” by Michael Bluejay:

“The Comparative Anatomy Of Eating”:

“A rational critique of the talk: ‘Humans Are Omnivores’ adapted from a talk by vivisectionist John McArdle, Ph.D” – by Laurie Forti:

“Whatever Happened To Omnivora”:

“Taxonomy vs. Diet”:

“Science Verifies That Humans Are Frugivores”:

“20 Questions On Atherosclerosis”:

“9 Reasons Your Canine Teeth Don’t Make You a Meat-Eater”:

“The Human Predator: Eyes in Front Explored – Mic The Vegan”:

“Beyond Polemics”:

“Biological Adaptations”:

“Fossil Implies Our Early Kin Lived in Trees, Study Says”:

“Theories of Human Evolutionary Trends in Meat Eating and Studies of Primate Intestinal Tracts”:

“Planet of the Starch-Eaters”:

“The Ancient Human Diet Is Starch-based”:

“Chimpanzees use botanical skills to discover fruit”:

“Relating Chimpanzee Diets to Potential Australopithecus Diets”:

“Diet and seasonal changes in sympatric gorillas and chimpanzees at Kahuzi–Biega National Park”:

“Evolution and Prostate Cancer”:

The misc. medical info:

If you’re not already Vegan, and you think animals matter morally, then please go Vegan. It’s incredible for the animals, easy and great for you, and wonderful for the planet. If you’re already Vegan, please educate non-Vegans about why they should go Vegan. Please rescue, volunteer, adopt, foster, spay, and neuter the nonhuman refugees of domestication whenever you can. Please feed your nonhuman family Vegan where you can. These things are the most important, morally responsible things to do and are desperately needed by everyone.

To learn more about Abolitionist Veganism and the issues I’ve outlined in this post, check out The Master List Of Vegan Info:

Disclaimer: My only goal with this list is to produce as comprehensive a resource for Vegan information as possible. I am 100% Abolitionist Vegan and 100% against exploitation of nonhuman or human animals, any type of violence against human or nonhuman persons or property, welfare regulation, any form of speciesism, ethnic bigotry, genderism, ableism, heterosexism, etc., any of the large governmental or non-governmental nonhuman animal organizations, “happy meat,” vegetarianism, veg*nism, Meat-Free Mondays, or other forms of reductionism and anything else that makes it seem like any form of violence or exploitation of animals is ok. If any of those positions are endorsed on any site in this list, or any language is used to imply that, it’s not that I included that link because I agree, but simply because I don’t control every bit of information on all of these sites.


13 thoughts on “Humans Are Naturally Herbivores

  1. Pingback: Master List Of Vegan Info | The Legacy Of Pythagoras

  2. Pingback: My Personal Ethos: The Legacy’s Stance On Animal Rights | The Legacy Of Pythagoras

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  4. Pingback: Do Doctors And Other Scientists Still Think Animal Substances Are Healthy? | The Legacy Of Pythagoras

  5. If physiology determines whether an animal is a herbivore, omnivore or carnivore, then why would humans have enzymes that break down fats and proteins if they weren’t meant to consume animal products? Also, why is there no naturally occurring plant source for Vitamin B12? If there was no civilization or, grocery stores in particular, and there wasn’t every possible plant source available all the time, would humans really be able to sustain their caloric and nutrient needs off whatever local vegetables were available? According to evolution, humans would not have protease and lipase enzymes to breakdown animal products if we did not need them. Animal products are not toxins, they do not kill cells in our bodies upon contact. Over time diseases develop because people eat too much animal product in their diets, that does not mean they’re toxic. That would be like saying water is toxic because you can cause dilutional hyponatremia. I believe that most of us, especially Americans, eat way too much meat. I think we should consume animal products a few times week, maybe once a day and we’d be much more balanced. To say that we weren’t meant to eat animal products whatsoever and claim that its toxic is misleading. If you have to buy a supplement to meet a requirement, then that is obviously not a natural part of the diet.

    • “If physiology determines whether an animal is a herbivore, omnivore or carnivore, then why would humans have enzymes that break down fats and proteins if they weren’t meant to consume animal products? According to evolution, humans would not have protease and lipase enzymes to breakdown animal products if we did not need them.”

      That argument only works if fats and proteins do not exist in plants. Is that what you’re claiming? Protease and Lipase enzymes are not specifically only for digesting animal substances, and even if some of them were, it could be argued that we could have adapted some of the enzymes we had to digest plants to this purpose… except that the science on this subject shows us that every other adaptation we have regarding digestion of flesh and dairy skew away from Carnivora. Animal flesh still does not completely break down in the human colon, and our digestion time is much longer than that of a Carnivoran. Around 40% of humans are lactose intolerant, and 60% do not maintain the ability to digest lactose past childhood. It’s exceedingly likely that humans have merely begun adapting to the fact that we’ve been irrationally forcing ourselves to consume unhealthy substances, but this is far from a recommendation for doing so.

      Also, I would caution against using the word “meant” unless you’re arguing creationism. We’ve adapted, through natural selection, to be able to metabolize certain nutrients more efficiently, and some less efficiently. There is no such thing as being meant to do so.

      However, it takes a lot longer than we’ve been consuming animal flesh for any organism to go from herbivore to non-specified carnivore. You might want to read this to understand my wording:

      “Animal products are not toxins, they do not kill cells in our bodies upon contact. Over time diseases develop because people eat too much animal product in their diets, that does not mean they’re toxic.”

      You’ve just described, almost faultlessly, the difference between acute toxicity and chronic toxicity, and validated my claim that animal substances are chronically toxic to humans.

      I think you should reread the piece, since I explain quite thoroughly why it takes more than a few seconds to poison yourself with flesh, dairy or eggs. If I didn’t know better, I’d almost think you didn’t read the piece at all…

      “That would be like saying water is toxic because you can cause dilutional hyponatremia”

      No, it’s saying exactly that. You do understand that aven an excess of plant substances of any kind, just like any substances, are capable of harming is, right? In this issue, the key is in how much harm is done over what rate of time. We’re talking about OPTIMAL diet. I never made the claim that you can’t live to X age or won’t avoid X disease while still consuming X amount of flesh, dairy or eggs. What I’m saying is that we’re herbivores because we won’t live for the length of time LONGER that we would have and avoided the diseases we DO develop at the latter stages of life had we not consumed animal substances.

      None of this addresses the fact that it’s incredibly immoral for humans to intentionally exploit nonhumans for any reason, as proven concretely here:

      Your assertion that “we should eat meat” is still nullified by that fact.

      “If you have to buy a supplement to meet a requirement, then that is obviously not a natural part of the diet.”

      All humans in developed countries are already supplemented with vitamins and minerals, since the institutional exploiters of nonhumans supplement their feed and add nutrients to milk that you drink:

      B12 and D do not occur in unsupplemented nonhumans in a high enough amount to keep non-Vegans healthy by exploiting them. So your Appeal To Nature fallacy has been neutralized by your very own argument.

      “why is there no naturally occurring plant source for Vitamin B12?”

      You do know that B12 does not originally come from animals, right? The only reason any animals have any B12 inside them at all is because we consumed vegetables and other plant foods with bacteria on them, mainly from feces. If you’re interested in learning about what the real truth about B12 is:

      Sub-Section 2B4c:
      Myths About B12:

      “Vitamin B12 Deficiency—the Meat-eaters’ Last Stand”:

      “Vegan B12 deficiency: putting it into perspective”:

      “Vegan Sources”:

      “Vitamin B12: Are You Getting It?”:

      “B12 in Plant Foods”:


      “The Vitamin B12 Issue”:

      “Vitamin B12 recommendations for Vegans”:

      “Forum: B12 in plants?”:

      “More on nutrition”:

      “Vegans and the Vitamin B12 Deficiency Myth”:

      “Vitamin B12 and Human Nutritional Evolution”:

      You’ve actually given me more to add to the above post, so thank you.

  6. Pingback: My Personal Ethos: The Legacy’s Stance On Animal Rights | The Legacy Of Pythagoras

  7. Then why do I bloat horribly in the face and stomach from all green vegetables, a lot of fruit, all berries, all tree-nuts and most grains, am I not human?

    • Before I give you the secret to your dilemma, let me ask you a question. How much have you studied biology, specifically the role of what we eat in relation to our physiology? And a follow-up: are you seriously interested in learning about this, or just in arguing against Veganism?

  8. Pingback: Health-Related Information On Plants-Only Diets | The Legacy Of Pythagoras

  9. Pingback: Are Humans Omnivores? – Dr. Green, N.D. & Associates

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