Skip to main content

Debate: Are Humans Omnivores?

Interview With a Vegan Paleontologist: “The Humane Hominid”

Robert, aka “The Humane Hominid”, is the vegan paleontologist behind PaleoVeganology, a blog that looks at the evolution of humans and animals, as well as the paleo diet movement, from an ethical vegan perspective.

Robert went vegetarian in high school “to impress a pretty girl,” and stayed that way for the animals. He has been vegan for six years. This didn’t stop Hurricane Ivan from destroying most of his worldly possessions 2004, so he moved to Los Angeles, figuring that he might as well enjoy nice weather while natural disasters nipped at his heels. He got a spec screenplay optioned not long after moving to earthquake country, but Hollywood was only getting his hopes up in order to dash them (as it tends to do), and Robert gave up that dream to return to paleontology school.

The vegan blogosphere is lucky he did. PaleoVeganology is everyone’s favorite vegan paleontology blog, and is one of the most important contributions to the burgeoning “vegan skeptic” movement — the ethical vegan reformers who are more than happy to hack down fallacious arguments for veganism, like the myth that humans are naturally herbivores. To this end, Robert is currently engaged in an online debate with “The Permavegan,” a vegan permaculture advocate who believes that it makes no biological sense for humans to eat meat.

I have my money on Robert. 

Are humans “omnivores”?

Yes, unequivocally.But I’m glad you put that word in scare quotes, because it’s possible for people to read too much into it. The description of humans as “omnivores” is observational, not taxonomic, and definitely not prescriptive. When researchers into human evolution use that word, they mean something a bit different than what, say, paleo dieters or other carnists do. Omnivory does not impose behaviors on us; it’s merely a description of our capabilities and our morphology. We’re neither specialized plant-eaters nor specialized meat-eaters.From the perspective of morphology, it can’t be inferred that we must eat either plants or animals, only that we can eat them both.

Why do you refer to meat-eating humans as carnists?

Honestly, because I just think it’s a cool word, and I am often too lazy to type out the phrase “meat-eating humans.” The word has its origin in the effort by some vegans to label those humans who continue eating meat after being exposed to cruelties of factory farming; i.e., those who eat meat because of a conscious ethical choice, and not out of habit. A carnist is someone committed to the ideology that it is acceptable to eat (some) animals, and is basically the opposite of “vegan.” But like I said, I mostly use it because I think it’s a cool word and a practical shorthand device.

It’s obvious that you are not using your blog to try to prove that veganism is our “natural diet”. What would you say your message is? That evolution is complicated and it doesn’t make sense to try to base lifestyle choices on it?

That’s part of it. Though it’s not just that evolution is complex – far more complex than most people realize, actually – but also, paradoxically, that it’s limited. Evolution is a great tool for figuring out the ancestry of organisms and the mechanisms of speciation and such, but it’s fundamentally about populations, not individuals. As such, it’s not a great guide for figuring out what your “optimal” diet is. The human fossil record is too sparse for that, and even if it were more robust, I think it’d be problematic at best to try to base ethical or lifestyle choices on it.

I should confess here that the “message” of my blog is itself evolving. I started it because I kept running into vegans who, upon learning I was a paleontology student, would ask me for rhetorical ammo to use in their own arguments against eating animals. It’s common for vegans to argue that “humans are natural herbivores,” for instance. But things just aren’t that simple. At first, I was game for the effort, but by the time I decided to start blogging, I had become more skeptical of it.

At present, I’d say the message of my blog is that veganism is, first and foremost, an ethical stand, and should, first and foremost, be argued and defended as such. Paleontology and evolution can bring a great deal of clarity to our understanding of issues related to veganism and animal rights, but they can’t by themselves be used to build a case for (or against) veganism and animal rights.

Does our evolutionary heritage provide any clues for healthier ways for us to live?

Only in the negative sense of showing us what we can’t do, at present, and not in the positive sense of showing us what we should do.

I’m glad you asked this question, too, because it touches on a fundamental, though very common, misunderstanding of evolution. Natural selection is about constraints on species development, and whether species develop adaptations to get around those constraints. It doesn’t have anything to do with individual health.

There’s a notion going around in many diet and health subcultures that evolution “wants” (for lack of a better word) us to live long and healthy lives, and that if we can just discover the right combination of foods and exercises, we’ll unlock our boundless potential.

But that’s not how evolution works. It doesn’t give a shit about your quality of life. It only wants you to make as many babies as possible, and make sure they reach reproductive age. This means that an out-of-shape, SAD-eating, chain-smoking, alcoholic, meth-addicted slob who lives half as long but has twice as many babies as a vibrantly-healthy vegan or paleo dieter is more fit than either of them, in evolutionary terms.

Natural selection imposes constraints on our development as a species, which can certainly have health consequences, but it has not and will not do us any favors. There’s no design for “optimality” or perfection hidden in our genes. Nature wants us to screw and die. That’s it.

Some people thrive on a vegan diet and some people do not. Do you think this is all psychological, or could genetics play a part? Could some humans have a biological requirement for animal products to thrive, while others do not?

I don’t want to paint myself into a corner and say that veganism will work for every single person on the planet; after all, nature confounds our categories, and variation abounds. Having said that, though, humans are not snowflakes. We are still primates and are still subject to many of the dietary constraints that nature imposes on all other primates.

It’s conceivable to me that there are, at the present time, some humans who cannot thrive on healthily-structured vegan diets. But that’s unlikely, in my opinion, to be because of a dietary requirement for animal products per se. Certainly, we have a biological requirement for specific nutrients, but I’m skeptical that anyone has a requirement for specific nutrient sources. There’s nothing magical about meat and dairy. One day, science will figure out the mechanisms imposing those constraints, and then figure out ways around them. And then, those types of people currently “stuck” with animal products will be able to thrive as vegans, too.

Nonetheless, I do suspect these kinds of people are in the minority. I think a lot of ex-vegans should be skeptical of themselves and inquire whether they engaged in the tendency of diet subcultures to self-diagnose, and thus misinterpreted the data about themselves. They may have attributed a pre-vegan condition or deficiency to veganism itself. As one example, B-12 deficiency is common in the general population, not just among vegans. If the Framingham study is a good indication, about 16 percent of the public may be experiencing undiagnosed B-12 deficiency, and about 39 percent are in the “low-normal” range, which constitutes a deficiency for some people. Many people who go vegan and experience B-12 deficiency symptoms may have been deficient before they went vegan, even if they only experienced symptoms after. But they will self-diagnose and blame veganism for a pre-existing problem they didn’t know they had.

I think we should also consider the possibility that a lot of ex-vegans didn’t just go vegan, but also signed on to one of the fringier elements of the vegan community, like raw veganism, or low-fat veganism, or fruitarianism (or all three!), which take a lot more effort and have a lot less long-term health viability. Or conversely, they may have been a junk-food vegan and adopted the mindset that since they’re vegan now, all their health troubles are over.

Obviously, medicine and nutrition are not my specialty, but I have a hard time swallowing the idea that there’s some ineffable quality about animal products that prevents a majority of people from getting those nutrients through supplements or high-quality plant sources. I’m inclined to think that if the majority of these ex-vegans had found Jack Norris or Ginny Messina before deciding veganism wasn’t working, they’d have turned out just fine. And those populations for whom veganism isn’t currently viable will one day have the option, too. Science marches on!

If not being specialized plant or meat eaters theoretically makes it possible for humans to choose an all-vegan diet without significant health consequences, would the same hold true for choosing an all-carnivorous diet?

First, I’m not convinced it’s possible to choose any diet “without significant health consequences.” I contend there’s no such thing as an “optimal” or “perfect” diet. Nature doesn’t work that way. I think no matter what you do, you will always have diet-related health issues to deal with.

Second, while it’s true that humans are flexible, we are not infinitely flexible. Natural selection is conservative, and still imposes constraints on us. We may be better at digesting animal products than other primates, but that doesn’t mean we’ve stopped being primates. It’s pretty clear that humans in general do best, health-wise, when they eat a diet high in plants and moderate in animal sources. We are by no means “natural” vegans, but we’re closer to that on the spectrum than we are to being “natural” carnivores. In short, I think an all-meat diet would have more health issues to get around than an all-vegan diet, though neither of them is “optimal.”

What do the paleo diet people have wrong?

I think the historical narrative underlying the paleo diet is a just-so story bolstered by the naturalistic fallacy and embellished with noble savage fantasies of a golden age.This is not to say that it’s a bad idea to eat less processed food, or that we don’t face health problems unique to our era. But the notion running through so much of the paleo diet movement that there was a long-lost health utopia in which flint-knapping personal trainers wandered the Pleistocene with an ethic of enlightened stewardship, is rubbish. As is the idea that we can recover or recreate that lost age in the modern world.

No one who actually studies the fossil or archaeological record with any rigor could swallow that narrative; we’ve seen the diseased hominid teeth and bones for ourselves; we’ve uncovered the kill-sites where whole herds were driven over cliffs just to claim the meat and skins from a few individuals. We know that humans are like all other animals: they over-breed and consume resources with abandon, unless checked by survival pressures. This has always been true.

The paleo diet movement began with a basically reasonable idea – that maybe we should try to mimic the diet of our ancestors, since we inherited traits from them that will influence our own health – but seems since then to have contorted itself into a grain-phobic meat cult based on a vision of human evolution that has no resemblance to what the fossil record tells us about ourselves. No paleontologist or anthropologist doubts that hominins ate meat – and, during the Ice Age outside of Africa, probably quite a lot of it – or that doing so shaped our evolution, but we’re not obligate carnivores who evolved in high latitudes. We come from the African tropics, and the ancestors from whom we inherited the plan for our digestive and masticatory traits are generally considered to have been largely frugivorous. Some australopithecine fossils even show evidence of grass consumption.

But you know what? Even saying that isn’t precise enough, which is another major gripe I have with the paleo diet (and with many vegans, too). Paleo dieters are always pointing to our “evolutionary heritage” for hints about the “optimal” diet, but no one ever seems to be more specific than that. Which hominin species are you counting as ancestral to us? Which traits on your laundry list of “proof” are primitive and which are derived? Do you even understand what that question is asking and why it’s important? If someone making evolutionary claims can’t answer these questions, I for one see no reason to take their opinion seriously.

It’s a bit like listening to New Age gurus invoking quantum mechanics, or young Earth creationists appropriating the lexicon of geology: to the average person, a string of smart-sounding words from such types can sound impressive; but to someone with even a bit of training in the relevant field, it sounds like nonsense.

Finally, I’m a bit territorial about the nick-name “paleos”; paleontologists gave themselves that nick-name a long time ago, and now these dieters are trying to muscle in on our turf. I won’t have it!

In a recent entry you wrote that an adaptation for fruit eating accidentally made humans better at digesting meat. How are fruit eating and meat eating related?

Fruigvory is our base gut adaptation, but it’s flexible enough to allow primates to digest meat, especially cooked meat. When our lineage adopted a greater degree of carnivory as a survival strategy, nature selected for those variations of the base “frugivorous” gut that were slightly better at meat-digestion. But just because we got better at eating meat, that doesn’t mean we got worse at eating fruits, seeds and foliage. We didn’t specialize to become obligate carnivores.

To give your readers some context, I’ve been having an ongoing debate with the Permavegan, Jonathan Maxson, over his hypothesis that meat was a fallback food of last resort for prehistoric humans. At that particular stage in our debate, I perceived him as trying to draw a distinction between “frugivores” and “omnivores,” the implication being that if humans were the former, they couldn’t be the latter. I’m not now so certain that’s what he was doing at all (I’ll have to wait and see), but in any case, I cited Hladik, et. al.’s critique of the expensive-tissue hypothesis as a counter to this perceived claim. Their point was that human gut morphology, being unspecialized, was best described as “frugivore,” a flexible trait which allowed humans to feed extensively on animal matter. I summarized their point as follows:

In other words, modern human guts are adapted to a diet of soft, energy-dense foods, a condition they inherited from “frugivorous” ancestors but that accidentally also allows them tobe better at digesting meat than other primates. To put it succinctly, H. sapiens are functionally omnivorous becauseof their frugivory, not in spite of it (a point that threatens to undo thewhole debate before it even starts)!

What I’m pointing to here is the concept of exaptation, wherein a trait developed in response to one survival pressure gets passed on to distant descendants no longer facing that pressure, who co-opt it for another use. The use to which they co-opt it, however, isn’t the use for which it was “meant”; it just happens to be flexible enough to be useful for several things.

In that debate, I’m arguing to a fellow vegan that a human “fruigvorous” adaptation doesn’t preclude an ability to be good at eating meat. If I were debating a carnist on the same point, I’d say that just because humans can digest meat, that doesn’t mean we “evolved to” do so; it just means we found a new use for a flexible trait common to “frugivorous” primates.

Has studying paleontology caused you to re-think any aspects of your views on veganism?

Definitely! I used to be one of those vegans who argued that humans are natural herbivores, and was quite happy with myself for having memorized the laundry list of traits that supposedly “proved” it. Once I really began to understand evolution, though, I became far more circumspect about that tactic. Just because we possess a trait does not mean that trait evolved to suit us in particular, for the way we use it in particular. It certainly imposes no dietary obligations on us. I think vegans and paleo dieters alike should take that to heart.

Ironically, my coming to understand that evolution, by itself, isn’t a great basis for making the case for veganism led me to a deeper appreciation for the moral and ethical arguments for veganism. I didn’t read Peter Singer or Tom Regan until after I’d read Stephen Jay Gould and Richard Dawkins.

What should paleontology inspire meat eaters to re-think?

The ecological sustainability of a widespread human diet centered on eating animals… and that includes hunting. I know it’s all the rage to vilify Neolithic agriculture and monocrops and such – and there are certainly legitimate and profoundly important issues there – but really, the record of Paleolithic hunter-gatherers isn’t too admirable, either. Look at Paul Martin’s work on the Ice Age mammal extinctions; I think he’s right – and I’m far from alone – that the most parsimonious explanation for the disappearance of big mammals (especially outside of Africa) at the Pleistocene-Holocene transition is human over-hunting. During the Paleolithic, the world lost 85 percent of mammal species larger than 44 kg, including several keystone predators whom we either killed off or out-competed.

This had enormous ecological impacts: it sparked several secondary, localized extinctions and altered seed-dispersal patterns worldwide. We were able to weather that because our population was so small and scattered, but it’s in our nature – like most other animals – to overbreed and overeat, and with the current human population and rate of species extinction, we can afford neither to keep doing things as we do them now, nor to go back to the supposed good-ole-days of the hunter-gatherers.Both legacies are recipes for catastrophe. We have to figure out something new.

Do you have any ideas for what the something new should be?

Well, veganism, of course. A lot of veganism’s critics like to proclaim, “there’s never been a vegan culture,” and as far as I can tell, they are right. But that’s not an argument against creating one now.

I’m not yet learned enough to give specifics, but in general outline, I think we should endeavor to create a civilization that uses other animals as minimally as possible while “re-wilding” a number of lost habitats. I doubt that will mean universal veganism in the sense that no one anywhere ever uses any kind of animal product or labor ever again, but to my mind it’s indisputable that many of our most pressing ecological concerns are rooted in our exploitation of animals. Unless we come to terms with that and own up to it and start thinking creatively about it, I think we’re screwed.

You wrote about a new theory that humans adapted an empathy toward animals in order to be better able to procure meat. By knowing more about animals, as well as domesticating animals to be used in part as hunting tools, humans increased their hunting prowess. As you pointed out, this seems to lead to a paradox: meat eating and empathy with animals were dependent on each other, but the empathy that made it easier for us to eat meat now sometimes makes us feel like it is wrong to do so. Domesticating animals that we bond with in order to hunt wild animals also relates to a paradox that a lot of vegans decry: “Why love one and eat the other?”

What significance do you see in this theory, if correct? Could “moral schizophrenia” — loving one and eating the other — be in our genes? If so, could that mean the idea of “humane meat” and eating animals while loving other animals is not as ridiculous as some vegans say?

I think you’re not doing Pat Shipman’s theory enough justice! She’s claiming that empathy for other animals wasn’t just a useful trait, but that it actually drove our evolution. I think that’s a profound claim, and I ordered her book so I can get a better handle on all the nuances.

The significance of her hypothesis is its elegant simplicity; it’s always been clear that the invention of stone tools, the emergence of symbolic expression (ultimately becoming language), and the domestication of nonhuman animals were important events in human evolution, but no one could ever decide which one was most important to our development. Now Shipman comes along with a simpler proposal: that all three are consequences of a unique human ability to empathize with other animals, and in squabbling over them, we’ve been missing the forest for the trees. Her initial review article was published with mostly positive feedback from other researchers, and I’m looking forward to the more fleshed-out version in her book.

I have no problem with the idea that it’s possible for meat-eaters to genuinely love animals, even animals they have raised and slaughtered themselves. Such “moral schizophrenia,” as you put it, likely is an expression of ancient and deep-seated traits. But, as with all other traits, one shouldn’t read too much into this. It doesn’t mean that the “humane meat” position is more, or less, valid than the animal-rights vegan position. The “humane meat” position and the animal liberation position would both be expressions of the same primal trait, and thus, equally ridiculous!

Evolution will not give us easy answers to animal rights questions. That comes down to ethics, in the end.

Image courtesy of


Popular Video