Home » Brain size » Vegans/Vegetarians vs. Carnivores and the Neanderthal Diet

Vegans/Vegetarians vs. Carnivores and the Neanderthal Diet

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The vegan/vegetarian-carnivore debate is one that is a false dichotomy. Of course, the middle ground is eating both plants and animals. I, personally, eat more meat (as I eat a high protein diet) than plants, but the plants are good for a palate-switch-up and getting other nutrients in my diet. In any case, on Twitter, I see that there is a debate between “carnivores” and “vegans/vegetarians” on which diet is healthier. I think the “carnivore” diet is healthier, though there is no evolutionary basis for the claims that they espouse. (Because we did evolve from plant-eaters.) In this article, I will discuss the best argument for ethical vegetarianism and the evolutionary basis for meat-eating.


The ethical vegetarian argument is simple: Humans and non-human animals deserve the same moral consideration. Since they deserve the same moral consideration and we would not house humans for food, it then follows that we should not house non-human animals for food. The best argument for ethical vegetarianism comes from Peter Singer from Unsanctifying Animal Life. Singer’s argument also can be extended to using non-human animals for entertainment, research, and companionship.

Any being that can suffer has an interest in avoiding suffering. So the equal consideration of interests principle (Guidi, 2008) asserts that the ability to suffer applies to both human and non-human animals.

Here is Singer’s argument, from Just the Arguments: 100 of the Most Important Arguments in Western Philosophy (pg. 277-278):

P1. If a being can suffer, then that being’s interests merit moral consideration.

P2. If a being cannot suffer, then that beings interests do not merit moral consideration.

C1. If a being’s interests merit moral consideration, then that being can suffer (transposition, P2).

C2. A being’s interests merit moral consideration if and only if that being can suffer (material equivalence, P1, C1).

P3. The same interests merit the same moral consideration, regardless of what kind of being is the interest-bearer (equal consideration of interests principle).

P4. If one causes a being to suffer without adequate justification, then one violates that being’s interests.

P5. If one violates a being’s interests, then one does what is morally wrong.

C3. If one causes a being to suffer without adequate justification, then one does what is morally wrong (hypothetical syllogism, P4, P5).

P6. If P3, then if one kills, confines, or causes nonhuman animals to experience pain in order to use them as food, then one causes them to suffer without adequate justification.

P7. If one eats meat, then one participates in killin, confining, and causing nonhuman animals to experience pain in order to use them as food.

C4. If one eats mea, then one causes nonhuman animals to suffer without adequate justification (hypothetical syllogism, P6, P7).

C5. If one eats meat, the one does what is morally wrong (hypothetical syllogism, C3, C4).

This argument is pretty strong, indeed it is sound. However, I personally will never eat a vegetarian/vegan diet because I love eating meat too much. (Steak, turkey, chicken.) I will do what is morally wrong because I love the taste of meat.

In an evolutionary context, the animals we evolved from were plant-eaters. The amount of meat in our diets grew as we diverged from our non-human ancestors; we added meat through the ages as our tool-kit became more complex. Since the animals we evolved from were plant-eaters and we added meat as time went on, then, clearly, we were not “one or the other” in regard to diet—our diet constantly changed as we migrated into new biomes.

So although Singer’s argument is sound, I will never become a vegan/vegetarian. Fatty meat tastes too good.

Nathan Cofnas (2018) argues that “we cannot say decisively that vegetarianism or veganism is safe for children.” This is because even if the vitamins and minerals not gotten through the diet are supplemented, the bioavailability of the consumed nutrients are lower (Pressman, Clement, and Hayes, 2017). Furthermore, pregnant women should not eat a vegan/vegetarian diet since vegetarian diets can lead to B12 and iron deficiency along with low birth weight and vegan diets can lead to DHZ, zinc, and iron deficiencies along with a higher risk of pre-eclampsia and inadequate fetal brain development (Danielewicz et al, 2017). (See also Tan, Zhao, and Wang, 2019.)


Meat was important to our evolution, this cannot be denied. However, prominent “carnivores” take this fact and push it further than it goes. Yes, there is data that meat-eating allowed our brains to grow bigger, trading-off with body size. Fonseca-Azevedo and Herculano-Houzel (2012) showed that metabolic limitations resulting from hours of feeding and low caloric yield explain the body/brain size in great apes. Plant foods are low in kcal; great apes have large bodies and so, need to eat a lot of plants. They spend about 10 to 11 hours per day feeding. On the other hand, our brains started increasing in size with the appearance of erectus.

If erectus ate nothing but raw foods, he would have had to eat more than 8 hours per day while hominids with neurons around our level (about 86 billion; Herculano-Houzel, 2009). Thus, due to the extreme difficulty of attaining the amount of kcal needed to power the brains with more neurons, it is very unlikely that erectus would have been able to survive on only plant foods while eating 8+ hours per day. Indeed, with the archaeological evidence we have about erectus, it is patently ridiculous to claim that erectus did eat for that long. Great apes mostly graze all day. Since they graze all day—indeed, they need to as the caloric availability of raw foods is lower than in cooked foods (even cooked plant foods would have a higher bioavailability of nutrients)—then to afford their large bodies they need to basically do nothing but eat all day.

It makes no sense for erectus—and our immediate Homo sapiens ancestors—to eat nothing but raw plant foods for what amounts to more than a work day in the modern world. If this were the case, where would they have found the time to do everything else that we have learned about them in the archaeological record?

There is genetic evidence for human adaptation to a cooked diet (Carmody et al, 2016). Cooking food denatures the protein in it, making it easier to digest. Denaturation is the alteration of the protein shape of whatever is being cooked. Take the same kind of food. That food will have different nutrient bioavailability depending on whether or not it is cooked. This difference, Herculano-Houzel (2016) and Wrangham (2009) argue is what drove the evolution of our genus and our big brains.

Just because meat-eating and cooking was what drove the evolution of our big brains—or even only allowed our brains to grow bigger past a certain point—does not mean that we are “carnivores”; though it does throw a wrench into the idea that we—as in our species Homo sapiens—were strictly plant-eaters. Our ancestors ate a wide-range of foods depending on the biome they migrated to.

The fact that our brain takes up around 20 percent of our TDEE while representing only 2 percent of our overall body mass, the reason being our 86 billion neurons (Herculano-Houzel, 2011). So, clearly, as our brains grew bigger and acquired more neurons, there had to have been a way for our ancestors to acquire the energy need to power their brains and neurons and, as Fonseca-Azevedo and Herculano-Houzel (2012) show, it was not possible on only a plant diet. Eating and cooking meat was the impetus for brain growth and keeping the size of our brains.

Take this thought experiment. An asteroid smashes into the earth. A huge dust cloud blocks out the sun. So the asteroid would have been a cause of lowering food production. This halting of food production—high-quality foods—persisted for hundreds of years. What would happen to our bodies and brains? They would, of course, shrink depending on how much and what we eat. Food scarcity and availability, of course, do influence the brain and body size of primates (Montgomery et al, 2010), and humans would be no different. So, in this scenario I have concocted, in such an event, we would shrink, in both brain and body size. I would imagine in such a scenario that high-quality foods would disappear or become extremely hard to come by. This would further buttress the hypothesis that a shift to higher-quality energy is how and why our large brains evolved.

Neanderthal Diet

A new analysis of the tooth of a Neanderthal apparently establishes that they were mostly carnivorous, living mostly on horse and reindeer meat (Jaouen et al, 2019). Neanderthals did indeed have a high-meat diet in northerly latitudes during the cold season. Neanderthals in Southern Europe—especially during the warmer seasons—however, ate a mixture of plants and animals (Fiorenza et al, 2008). Further, there was a considerable plant component to the diet of Neanderthals (Perez-Perez et al, 2003) (with the existence of plant-rich diets for Neanderthals being seen mostly in the Near East; Henry, Brooks, and Piperno, 2011) while the diet of both Neanderthals and Homo sapiens varied due to climatic fluctuations (El Zataari et al, 2016). From what we know about modern human biochemistry and digestion, we can further make the claim that Neanderthals ate a good amount of plants.

Ulijaszek, Mann, and Elton (2013: 96) write:

‘Absence of evidence’ does not equate to ‘evidence of absence,’ and the meat-eating signals from numerous types of data probably swamp the plant-eating signlas for Neanderthals. Their dietary variability across space and time is consistent with the pattern observed in the hominin clade as a whole, and illustrates hominin dietary adaptatbility. It also mirrors trends observed in modern foragers, whereby those populations that live in less productive environments have a greater (albeit generally not exclusive) dependance on meat. Differences in Neanderthal and modern human diet may have resulted from exploitation of different environments: within Europe and Asia, it has been argued that modern humans exploited marginal areas, such as steppe environments, whereas Neanderthals may have preferred more mosaic, Mediterranean-type habitats.

Quite clearly, one cannot point to any one study to support an (ideologically driven) belief that our genus or Neanderthals were “strictly carnivore”, as there was great variability in the Neanderthal diet, as I have shown.


Singer’s argument for ethical vegetarianism is sound; I personally can find no fault in it (if anyone can, leave a comment and we can discuss it, I will take Singer’s side). Although I can find no fault in the argument, I would never become a vegan/vegetarian as I love meat too much. There is evidence that vegan/vegetarian diets are not good for growing children and pregnant mothers, and although the same can be said for any type of diet that leads to nutrient deficiencies, the risk is much higher in these types of plant-based diets.

The evidence that we were meat-eaters in our evolutionary history is there, but we evolved as eclectic feeders. There was great variability in the Neanderthal diet depending on where they lived, and so the claim that they were “full-on carnivore” is false. The literature attests to great dietary flexibility and variability in both Homo sapiens and Neanderthals, so the claim that they ate meat and only meat is false.

My conclusion in my look into our diet over evolutionary time was:

It is clear that both claims from vegans/vegetarians and carnivores are false: there is no one “human diet” that we “should” be eating. Individual variation in different physiologic processes implies that there is no one “human diet”, no matter what type of food is being pushed as “what we should be” eating. Humans are eclectic feeders; we will eat anything since “Humans show remarkable dietary flexibility and adaptability“. Furthermore, we also “have a relatively unspecialized gut, with a colon that is shorter relative to overall size than in other apes; this is often attributed to the greater reliance on faunivory in humans (Chivers and Langer 1994)” (Ulijaszek, Mann, and Elton, 2013: 58). Our dietary eclectism can be traced back to our Australopithecine ancestors. The claim that we are either “vegetarian/vegan or carnivore” throughout our evolution is false.

There is no evidence for both of these claims from both of these extreme camps; humans are eclectic feeders. We are omnivorous, not vegan/vegetarian or carnivores. Although we did evolve from plant-eating primates and then added meat into our diets over time, there is no evidence for the claim that we ate only meat. Our dietary flexibility attests to that.



  1. Samu says:

    I think the third premise in Singer’s argument is blatantly false (if I understood it correctly). “‘Equal consideration of interests’ is a moral principle that states that one should both include all affected interests when calculating the rightness of an action and weigh those interests equally.” It seems to me to be obvious that adults’ interests should not be treated equally to the interests of children, for example. Children should be given preferance. I think this also applies to humans over animals. This is a first principle, as far as I am concerned.

    I could also use a religious justification for it. God made animals to be ours, whether as food or as capital goods. Therefore it is okay to use animals in such manner.


  2. Crime Think says:

    Suffering is a human phenomenon. It comes from a perception of a Dasein, which is unique to humans.

    Animals experience pain. But this pain exists as a transitory signal and cannot be compared to the pain, and therefore suffering, experienced by a being that has a self. It cannot be compared as animals have no being that suffers, no self that exists across time that can suffer.

    (An interesting perspective that I’m borrowing. I suppose this could be refuted if you can prove the animal has a stable sense of self that carries through time. I don’t think that this has been done in the great apes. Interestingly, a very young child’s sense of self may not have this stability and expression as well. Food for thought.)


  3. King meLo says:

    These are all just so stories!!!

    All jokes aside though, I had originally answered the question “how can you tell trait x is an adaptation?” By providing genetic evidence, as you just did. You ignored it so our next discussion on the matter(the previous argument) I had assumed you must be meaning something else. Because even if you deny the genetic evidence you don’t have to call a trait an adaptation until it’s been identified to having an exogenous cause.

    Either way, I’m glad that you acknowledge there are scientific adaptionist hypotheses.

    Keep up the good work.


    • RaceRealist says:

      You never answered the question.


    • RaceRealist says:

      How would you test the claim that trait X is an adaptation? Meaning, supposed adaptation T, what evidence would raise the probability of the claim that adaptation T? (We can continue this on PP’s blog.)

      The evidence that we were meat-eaters is there – via Herculano-Houzel.

      Their work shows that meat-eating is what allowed our brains to grow as big as they did.

      I don’t need to invoke genetic explanations; I only need to invoke cooking denaturing proteins making food more bioavailable. Which is why I cited Carmody et al.

      The fact of the matter is: the ToNS is empty. One can invoke a developmental explanation, not even invoking NS. You know Fodor’s argument. Regarding cooking and the brain, basic logic indicates that, since cooking denatures protein and makes the calories more available along with the nutrients, this allowed our brain size to increase. Indeed, it was both necessary and sufficient.


    • King meLo says:

      Well then that just depends on the trait in question and does not refute anything. You more or less admit that there can be evidence for a trait being an adaptation. So there isn’t anything to argue about


    • RaceRealist says:

      Sure there is a lot to argue about. Coextensive traits, no laws of selection for. That doesn’t upend, of course, Herculano-Houzel’s data showing that cooking is both necessary and sufficient for brain size.


    • King meLo says:

      Well neither of those refute NS so I’m not concerned


    • RaceRealist says:

      Fodor’s argument does.


    • King meLo says:

      NS claims that some traits go to fixation because they facilitate reproductive success in an environment. Fodor’s point is that “thump thump” goes to fixation despite not having a function that causes fitness. NS does not inherently exclude this scenario therefore, the criticism is not a refutation.

      NS is supplementary. Don’t words matter?


    • RaceRealist says:

      Last response: without contextual laws of selection we cannot use NS to distinguish traits that cause fitness from traits that are correlated with fitness-causes.

      See you tomorrow buddy.


    • King meLo says:

      Well laws of selection exist but we don’t know all of them and probably won’t for a long time. This is a god of gaps type argument. Darwin would be rolling in his grave if he knew we were trying to make a “theory of beds” out of Evolution. Hence why i didnt really like this book.


  4. King meLo says:

    How does my response not answer the question? If my evidence is insufficient to satisfying the question so is yours for adaptations of a cooked diet. Either that or you’re wording your question completely wrong for what your trying to ask.


    • RaceRealist says:

      Trait T exists. Why does trait T exist? What evidence would be sufficient to explain the existence of trait T? Is the only evidence for the existence of trait T the data invoked to explain trait T? If so, it’s a just-so story.

      If not, it isn’t. Again: one doesn’t need to invoke selection. A DST perspective suffices.


    • King meLo says:

      A trait is not the same as an adaptation. A trait cannot be considered an adaption until it’s been proven to be one. For someone concerned with the precision of words you’re being very sloppy.


    • RaceRealist says:

      How can a trait be “proven to be an adaptation”? Fodor’s argument will continue to rear its head. In any case, let’s continue this on PP’s blog.


    • King meLo says:

      Fodor’s argument is not about whether we can differentiate between coextensive traits.

      Fodor’s argument is nowhere near as large as people think it is. The language just obfuscates the point.


    • King meLo says:

      We can continue this on his blog tomorrow. I want to relax. He takes to long to moderate and didn’t even think you’d be this engaging.


    • RaceRealist says:

      I’m relaxing right now too which is why I’m engaging like this.

      We’ll continue tomorrow my friend. Enjoy your night.


    • King meLo says:

      Well usually I get off to arguing but I had a long day at work so I’ma smoke a blunt and chill.

      You too bud.


  5. dealwithit says:

    you have not learned from valter longo rr-san.

    the best diet depends on age and activity.

    lots of meat while you’re still growing or maybe if you’re a serious strength athlete…otherwise a whole foods low protein plants based diet is best for almost everyone below age 70, at which point sarcopenia becomes a danger and animal foods should be eaten again.

    this isn’t even controversial anymore, because the mechanism is now known. it’s all governed by mTOR and IGF.


  6. dealwithit says:

    the obvious problem with the paleo-diet rationale is that while it is true that humans have not practiced agriculture or pastoralism long enough to adapt to it, it isn’t clear that humans and their ancestors have practiced meat eating long enough to adapt to it either. chimps get only about 3% of their calories from animals and gorillas and orangs get none. this fact should not be dismissed.


  7. dealwithit says:

    alcoholic beverages are calorie dense, protein free, and have a glycemic index and insulin index of 0.

    alcohol is a superfood…

    even though humans are no more adapted to it than they are to milk…much less adapted than pen-tailed treeshrews.

    that is, the best diet is composed of as much alcohol as can be tolerated…as much alcohol as does not cause the many health problems associated with it. this varies from person to person.


  8. dealwithit says:

    but it’s more complicated than that, because fasting is more effective at inhibiting mTOR and reducing IGF than veganism.

    in other words, the traditional inuit all-meat diet is even better than the colin campell diet provided it includes frequent fasting.

    but veganism is probably easier for most people than frequent fasting which is easier than veganism + frequent fasting.


  9. dealwithit says:

    in yet other words…if paleo people were serious they’d…

    follow a chimp diet, approximately…


    to the extent they consumed more meat, they’d fast more frequently.


  10. dealwithit says:

    protein is simply not a nutrient for fully grown people in the sense that there is no such thing as protein deficiency in adults who eat enough calories.

    and longo found that a low protein diet protected from cancer (reduced risk by 75%) and diabetes type ii (by 100%) and plant proteins are not as “accessible” as animal proteins…but then once one reaches old age he should start eating meat again.


  11. dealwithit says:

    but then lean body mass is the best thing for reducing mortality rate.

    so the best is to gain lots of muscle and then maintain it on a longo/campbell type diet.

    vegan bodybuilding is impossible and stupid.


  12. Dividualist says:

    I don’t understand what makes it a strong argument. Why would humans and animals deserve equal consideration? I don’t think even all humans do. This is just an assertion. Why does suffering imply moral consideration? Suffering is simply signal in the nerves that tells a being that it is getting damaged and better get out of there or do something. It is just feedback. The fact that beings avoid suffering, have a will, interest or desire to do so does not automatically imply whether you have to care about that or not.

    The whole thing is entirely confused. I think it is based on the liberal fallacy that will is somehow sacred, if a being wants something then it implies it should get it. And the equal consideration of animals and humans or even all humans is entirely unfounded. The obvious solution for the trolley problem ever normal person naturally takes is to run a quick calculation of how much he values those people. Equality is a modern myth without any reason other than it is rooted in the Christian idea that all people have souls (but animals not).


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