What did humans evolve to eat?

What did humans evolve to eat?

What did humans evolve to eat?

The human brain is the obvious smoking gun that answers the question: what did humans evolve to eat?

The vast size and energy demands of the human brain required a diet that differed from that of our hominid ancestors.

Are we herbivore vegans or carnivore wolves?

I see infographics like these posted in facebook groups and instagram feeds that try and make arguments that we are meant to be plant-eating herbivores or we are meant to be meat-eating carnivores. 

herbivore argumentcarnivore argument

Without fail the information that supports the argument is cherry-picked and that which doesn’t is omitted. There are almost always half right and half wrong. Because what is almost always omitted in both cases is the big picture.

Our Evolutionary Ancestors

Humans, the genus Homo, evolved from early hominids that lived in the trees, ate fibrous plants, and were undoubtedly herbivores. Our heritage is from the great apes, and our digestive tract would not have allowed a meat-heavy diet. We had large cecums that turned fiber into fat. This was our main source of energy. Too much meat would have twisted the colon and been extremely painful and even life-threatening.

Forced Change

Climate and environmental changes about 3 million years ago brought us to a crossroad. As rains became more scarce so did high-quality plants. Forests became wooded grasslands, and more grazing animals populated savannas. We had to diversify our diet – with meat – or compete for a dwindling limited resource – plants.

The asutralopiths, our hominid ancestors chose to stick with plants and became extinct.

Humans chose to venture out, take a risk, and incorporated meat into the diet.

Bad Hunters

When we left the trees for the grasslands, we were untrained and ill-equipped hunters. We were also easy prey of fierce, well-trained predators. So we did the obvious, we scavenged. In the early goings, we were likely carrion feeders which means we ate on dead and rotting flesh. We’d let the professionals do the killing and we’d hurry in for the scraps and return to safety.

Killer Stomach

Although we weren’t great killers in the early get-go our stomachs evolved through natural selection to do pathogen fighting for us. Our stomachs became very acidic. The acid in our stomachs killed off pathogens that resided in the rotting animals we scavenged and it also enabled improved digestion of meat.

Acidic stomachs separate carrion feeders and carnivores from herbivores. The acid filters out the bad pathogens while facilitating digestion into the small intestines. Baboons for example, who are considered one of our closest relatives, have stomachs that are about 1000X less acidic than ours.

From Supplement to Staple

Meat started off as a supplement to our plant-based diet. As the weather and environment continued to change, so did our diet, and so did our evolutionary adaptations.

Meat fueled our unprecedented brain growth and cranial capacity. With this energy dense food, our guts shrank and brains grew. Eventually we could no longer meet our energy demands without meat. We became obligate meat-eaters.

Energy dense animal products were the only way we could survive, the only way we could meet our energy requirements, the only way we could feed our brains and bodies.

While we could still eat plants, they simply couldn’t fuel us themselves. We’d lost much of our fermentation ability (that could turn fiber into fat energy) that a big cecum allows for. We traded it for the ability to eat increasing larger amounts of animal meat to power an increasingly growing brain.

The evolutionary decision was choosing between a big brain (meat) or a big gut (plants).

Running Wild

As we became dependent on animals for food, natural selection further changed our bodies. As once poor hunters that were newly out of the trees and barely bipedal, we transformed into predator apes. We morphed into skilled hunters. Specifically, persistence hunters.

Because we chose meat and brains, evolutionary forces pushed for survival of the fittest hunters. Humans became, and are now, the only living primate adapted for endurance running. We developed a vestibular system and nuchal ligament for balanced running. Natural selection favored running enhancements like longer lower limbs with muscles like the glutes and tendons like the achilles.

Since we were no longer climbing trees the muscles in our shoulders decoupled, and we became rock throwers, then spear throwers, then baseball throwers.

Our feet evolved to absorb shock and the big toe came into alignment with the other toes as running became more important than grasping limbs. We evolved sparse and short body hair and millions of eccrine sweat glands to prevent hyperthermia.

Running from Herbivore to Carnivore

Our diet and anatomy changed step for step.

We started to share more features and habits with carnivores than our herbivore ancestors.

Unlike herbivores that graze and grind all day, we became intermittent eaters like carnivores.

Prey. Eat. Rest and Digest. Repeat.

Our gut mirrored a carnivore gut. Our cecum shrank to the point of being a useless vestigial appendage since we were no longer using it to digest plant materials like our herbivore ancestors did. Rather, our small intestines absorbed fat and protein extremely efficiently and we now share similar well-developed gallbladders to that of wolves and lions.

Since we stopped grazing and grinding all day, our facial anatomy changed as well. Our jaws main use became vertical up-and-down chewing rather than the side-to-side, rotary mechanism of herbivores.

In fact our digestive system evolved so much we became a definitive host for tapeworms. No, this isn’t the greatest of human adaptations, but we are the only other mammal besides obligate carnivores like lions and hyenas that can be a definite hosts for tapeworms.

Hangry Herbivores

I often see vegan arguments about our teeth. They look like herbivore teeth so we must be plant-based eaters.

Well, we are primates and our basic body is derived from this heritage. Therefore we have teeth similar to other apes in terms of size, shape and number. Yet we still have ridged molars like wolves instead of flat ones like sheep. We also have small canine teeth and relatively smaller jaws.


Humans started using tools millions of years ago and fire hundreds of thousands of years ago to kill, cut, and cook the meat. Less mastication forces were needed. Additionally, since canines were predominately defense and intimidation mechanisms, the smaller canine represents a shift in social structure and mating behavior that results from cooperation, communication, and a reduction in male-to-male conflict.

For similar reasons, we have nails instead of claws – because we are primates. Primates don’t have claws. In no way does this suggest we are designed for a plant-based diet. It suggest we are primates – which we are.

What about carbs?

As humans we can extract and use carbohydrates in plants – not cellulose though – and not efficiently. This is where humans differ from pure carnivores.

To me it’s clear we CAN eat plants and that we didn’t completely lose this ability from our evolutionary history. It is also clear that we have become ill-equipped to eat plants, some more so than others. Fiber is excellent evidence of how we’ve diverged from our herbivore ancestors as well as how poorly we use exogenous antioxidants. So just because we can eat plants doesn’t necessarily mean we should. We can drink alcohol and extract energy from it, but it’s also a neurotoxin.

Limiting things in which we have limited ability to tolerate is a smart idea.

What did humans evolve to eat?

Throughout human evolution we became more and more equipped to eat meat and less and less equipped to eat plants.

We evolved from a pure plant-eating heritage, and gradually evolved to supplement that plant-based diet with meat, which eventually led to complete dependence on meat for survival. Plants became the opportunistic supplement to a meat-based diet.

All was well in evolution until about 10,000 years ago.

At this time we shifted from a meat-based diet to a dramatic return to a plant-based diet with the Agricultural Revolution. Even worse, we started eating plants that we’d never eaten in history. The decline in nutrition sped up further with the industrial revolution, as we started modifying and refining plants as well as spraying, storing, and shipping our new food. Today most of our food is synthetic in some way.

We took food we’d become ill-equipped to handle through millions of years of evolution and made it our main dish. And we took meat which literally made us human and that we had evolved to depend on and labeled it dangerous and a health, cancer and heart disease risk.

Really our shrinking brains and modern diseases are less of a mystery and less complex then we try to make it.

34 Replies to “What did humans evolve to eat?”

  1. Thanks for supplying great science based info. Indeed very convincing. Next to that… Humans seem to be the only species who’s brain can burn on ketones as opposed to i.e. apes. IMO that is a smoking gun for fat burning and keto/carnivore feeding. Also fat contains per unit (weight) more energy than glucose. As bipedal creatures and being able to sweat provided humans the possibility to outrun (in endurance) any other prey.

    1. With “Prey. Eat. Rest and Digest. Repeat.” Intermittend Fasting became natural part of our lifestyle hence explaining the metabolic succes of this phenomenon.

  2. Vegans will always try to tell you that you can get all nutrients from plants and meat does not contain any nutrients you need which you cannot get from plants. This is a lie, b12, heme-iron, choline and collagen all come from animals and only animals. Choline and collagen are extremely essential for repairing tissue in the body.

    1. Kevin, this triggers the following question: could a lack of collagen due to plantbased diet explain raised level of cholesterol for bodily repair purposes?

    1. Ekaterina, Darwin’s theory of evolution has shown us that species evolve to fill niches in the food chain/web. Just as a bacteria does not need to be given permission to exist by behaving in a way that ensures it’s survival, all other organisms don’t need to be “entitled” to be as they have evolved. It’s true humans have engineered sophisticated ways to provide for their needs in ways that include civilisation and agriculture. So now we have engineered different ways to meet our nutritional needs. I myself and I hope many humans have come to love and respect other organisms and ecosystems. We all want them to be treated with respect. Should all animals become vegan to meet your view of how one should meet their nutritional needs? It’s a great pity that people use emotive terms such as “slaughter” to describe an activity that can be respectful, natural and life-giving (the ending of an animal’s life to provide human food) in order to evoke an entirely negative light (brutal, indiscriminate, violent killing) on what is a natural process of life. I respect other peoples choice to become vegetarian, vegan or whatever because these choices support diversity which is what underpins life on earth. If only we could all concentrate on what counts at the individual, species and community level: Respect. Respect all the food you eat, if your choice of diet is vegetarian, vegan, or omnivorous ensure that the land, animals and communities that provide those foods are treated in a humane and sustainable way.

    2. The intent wasn’t to say that humans are entitled to slaughter animals any more than a lion is entitled to slaughter a deer. it is more about how are bodies are designed to eat. You can reject nature, you can reject gender, you can reject capitalism, but it doesn’t change what works best for you physically.

      1. But we must reject where most meat comes from today whether evolutionary or not. It is unhealthy, full of things our digestive system is not equipped to process and therefore disease sets in. Its all well and fine to understand the evolutionary history of eating for humans. But capitalism,and profit seeking at the cost of human health is where we are at currently. If you choose to eat what has been so terribly modified for profit instead of ‘big brain’ or health, then you can begin to see why not eating meat is a survival mechanism in this post modern era.

        Eating the flesh of other animals now is developing a global resistance to the medicines we need to survive, all for profit (antibiotics). Its called factory farming and is the stuff you buy in mass consumption at the local grocery. Even your local farmers, as a way to avoid this, is impossible because they are owned by the profit mongers, and so must fatten, treat using things our bodies will suffer from ingesting.

        My position is a return to plant based eating, as it is exactly what the animals we already eat, consume. So cutting out the middle digestion, is AOK by many of us. The problem is full circle, what are we now feeding our animals? This is the bigger and more concerning problem globally. Animals must be permitted to eat their natural diet. Cows in most of the world do not when we look at the diets of beef cattle, milk for dairy, etc. its poisoned. I do not think I have to explain that one. Corn is not grass.

  3. Wonderful comments. How to do I get this point of view to my vegan daughter who argues that human sapiens are not evolved to eat animal flesh. Anthrology is an endearing interest for me so I cannot accept my daughter’s opinion

    1. I think the most important thing is education and learning about health (but also environment, sustainability, ethics, etc…) and when all sides are seen from an impartial place, I believe many would-be-vegans would reconsider.

    1. Since the agricultural revolution there are undoubtedly adaptations to gain some tolerance to these foods (lactose tolerance is a good example: https://www.kevinstock.io/health/should-you-eat-dairy/)
      However, evolutionary adaptations are a very long scale phenomenon and changes are gradual.

      Moreover, one of the biggest problems today is that so much of our food was invented in the last century (which we simply are not adapted to eat in any way).

  4. Question. With the teeth and digestion comparisons being in favor of vegetarian and carnivore respectively, you mentioned that they kinda only see half the picture. Is that what you meant by showing two different pictures? Saying that some people show one bit of evidence to make the whole case for either or both?

    1. No, I wouldn’t say teeth are “in favor of vegetarian” – I would say they are evidence of our primate ancestry (herbivore) with evidence of modifications over time that show we evolved towards a meat-based diet.
      But people use the fact that we are primates and thus have features or lack there of (like claws) related to this ancestry to try and convince people that we are meant to eat plants/not meant to eat meat.

  5. Great article.
    That first image about Carnivore and human teeth differences is really silly. We don’t need carnivore features to kill prey because we have tools and weapons. Even if we had evolved from a carnivore, we probably would have lost some of the carnivore adaptations.
    One thing I did not see mentioned is the stereoscopic vision of human eyes which is generally associated with carnivores (the old schoolkid mnemonic : ” eyes in front , kill and hunt. Eyes to the side, run and hide.” ).

  6. Thank-You Kevin !!
    My wife and I have always been careered physically hard workers. We both, for reasons due to a changing world, economy, medical and economical reasons, became slow and old …. gaining weight,losing muscle,,, growing old before our time …
    In less than a month on your “Carnivore” advice, we are feeling renewed and know we will heal to become again the people we were born to be.
    I believe it was in 1971, at age 18, I read “Atkins” first book, following a “keto” style diet —– first mistake, thinking different patterns of eating to be diets —–
    Food intake —- needs to be a new knowledge way of providing fuel for life —- diets are unhealthy, provided by corporate groups wanting to advantage of humans in poor health-mentally and physically for the growth of their bank accounts.
    We hope and pray, your words and knowledge become the new normal, so the human race survives.
    You are a professional at spreading your word, we would like to help, however possible.
    Thanks, again —— Alan + Lisa

  7. Regarding the comment about evolving back to herbivores, I read somewhere that our brains have shrunk 10% since the advent of agriculture. So yes, we could evolve into 😬And I would like to throw out an interesting case study. Robinson Crusoe was based on a real man who survived being stranded on an island for many years. When they found the now older fellow he was so fit he would chase down goats for food. He had to catch them for his young rescuers for they could not.

  8. Omg finally some common sense! Even medical professionals and professors are preaching this vegan plant-based propaganda.

    Also, a good response whenever vegans bring up our teeth and nails is to simply ask them “Why do you need sharp claws and teeth to shoot a bow and arrow?” It’s funny because they never know what to say back. While it’s true most carnivores have sharp claws and teeth, these are adaptations for killing prey, not eating meat. Humans don’t kill with our nails or teeth, so evolving big sharp ones would’ve been useless.

  9. This is a great article. I was always wondering, why people can be so ingorant in terms of what they eat, because poor animals are being slaughtered. We need meat, our children need meat to grow healthy. I am glad my mom knew that.

  10. I am writing a thesis on something towards this. I’ve done the 30 day challenge, I considered it a “reboot” to find out what my body responds to. I think due to us being Americans and us being “Muts” our original regions detour what we are suppose to eat. Plant/Animal or a combination.
    I would actually love to have an intellectual conversation on what more you researched and ultimately pick your brain.

  11. Can we get sources on what humans evolved to eat?

    I’m familiar with ETH (expensive tissue hypothesis), and it’s widely accepted in the scientific community. But it’s still a hypothesis, but it’s by far the best one to date.

  12. question
    I know that Australopithecus extinct because their unwillingness to take risks.But why many other our herbivore relatives managed to survive,it doesn’t make sense.

  13. Would the ability to manipulate fire not have greatly contributed to feeding the metabolic demands of a large brain? Cooking foods (such as grain, but meat and such too) obviously makes the energy inside more available to us.
    I think this is such a significant point in human history that was missed out/ignored in this otherwise well put together argument.

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