Is human vegetarian by nature?

In this brief guide, we will answer the query, “Is human vegetarian by nature?” and will discuss human evolution from herbivore to omnivore.

Is human vegetarian by nature?

Yes, humans are vegetarian by nature. Even though we’ve been dubbed “omnivores” for eating both plants and meat, we’re physiologically herbivores. Nuts, vegetables, fruit, and legumes form the foundation of a healthy vegetarian diet. If you want to eat like our ancestors, you can.

However, evidence shows that humans have eaten meat since the Paleotythic era. Homo erectus is the first member of the genus Homo that existed about 2 million years ago. It is believed that they could control fire to cook seeds and meat. The overall inference could be that early humans consumed a mixed diet at some point in time. However, the  timeline of events that brought about dietary changes remains an enigma. It is possible that the addition of meat to their diet occurred at a later stage as part of a survival strategy. The harsh winters must have compelled them to rely on animal food because plants were buried under snow. The stone tool butchery marks support the theory that early African hominids were carnivorous from as early as 2.6 Million years (1).

Is vegetarianism a logical choice, or is there another option?

There’s no more heated argument in the realm of nutrition than that between meat-eaters and vegetarians. In this Spotlight feature, we examine the question of whether or not humans were created to consume just meat and vegetables.

Plant-based diets are popular for a variety of reasons, some of which are purely health-related. On the other hand, some meat-eaters don’t give a second thought to whether they should or shouldn’t eat meat, while others will fight tooth and nail for the privilege of gorging themselves on animal flesh.

When it comes to deciding what to eat, passions may run high. Food is essential to our survival, and our primate brains still tell us that we must protect the sources of our food.

Even though meat-related ethics still matter, we’re less concerned about them these days because we’re more interested in their biology. For similar reasons, we don’t get involved in discussions about meat production’s impact on the environment.

Are we carnivores?

As for the first question, it seems to be a straightforward one from an anatomical standpoint. As carnivores, our teeth and intestines are inadequate for slicing into the meat. Is this what we are? That’s not us; our intestines aren’t long enough, and neither are our teeth perfect.

The human digestive system resembles the digestive system of herbivores more than carnivores. The human’s small intestine is longer like herbivores so that the bolus remains for a longer time in the system to undergo digestion. Carnivores have a larger stomach and a shorter small intestine. Hunters, like lions and tigers, pursue a kill once every few days. The large stomach stores food that these animals digest while resting. The stomach is highly acidic in these animals, unlike the human stomach that shows mild acidity. The carnivores need hydrochloric acid to digest meat protein and kill harmful bacteria in the meat. Anthropologists argue that human dentition resembles herbivores more than carnivores. The human molars are flat (to help in grinding plant products). Incisors are spade-like (to help in peeling and biting soft food). Premolars are flat and nodular (to help in “mulching” soft and smooth food) (1).

It would appear that we are omnivores, as our bodies are capable of digesting both animal and plant matter. But things are a little more complicated than this. It’s impossible to tell what an animal eats based just on its teeth and intestines. The panda, with its ferocious teeth and bamboo diet, serves as a good illustration of this kind of predator.

That being said, it is true that most animals have a digestive system that is adapted to their food. Large, smooth-walled stomachs like those of lions are ideal for storing large amounts of meat. Furthermore, many herbivores have enormous plant-destroying factories in their abdomens, where microbes break down the hard components of plant matter.

The human race likes to think of itself as unique and, in many respects, we are. Our internal tubing, however, is abysmal by comparison.

In a somewhat uninteresting way, the human digestive system is very much like that of primates and apes. If we want to function in harmony with our digestive systems, we should eat a diet that is at least comparable to that of our relatives.

Almost all monkeys and apes eat nuts, fruits, leaves, insects, and rare pieces of meat as their primary diet. Non-meat foodstuffs are much more common in the chimpanzee diet than adult chimpanzees eating infant chimps, which may be startling to some.

However, herbivores are most efficient in digesting plants and plant fibers—and carnivores the least. In contrast, microbes in the digestive system are most prominent in carnivores because they are needed to digest meat. When comparing humans and mammals, such as apes, the latter have a proportionally larger intestine. The small intestine and lack of cellulase make humans incapable of extracting plant nutrition. Another significant difference between herbivores and humans is the presence of foregut or hindgut in the herbivores (1).

Humans may be able to infer that evolutionarily speaking, we don’t need to be vegetarians and developed to ingest just a little amount of animal tissue on occasion.

Human development and the consumption of meat

Some evolutionary experts believe that early humans had an advantage because they were able to sustain themselves by eating flesh. Meat’s high levels of energy and protein may have aided in the growth and development of the large bundle of cabling between our ears. 

The brain size increase, coincident with a decrease in gut size, suggests an improvement in dietary quality. Whether such a diet quality change was accomplished with the aid of cooking or simply by advancements in stone tool technology, and whether meat or starch rich underground storage organs were the most critical high-energy food source in this scenario, is the subject of vigorous debates (2).

If we want a bigger brain we must save energy elsewhere, according to the pricey tissue theory. The procedure included shortening our intestines.

As a result, our food had to be of better quality to meet our dietary needs since our digestive tract was smaller. This is where a diet based on animal products comes in. Consider the fact that this hypothesis hasn’t been widely accepted. T. Bipedal posture and sophisticated civilizations may have been aided by hunting prey, according to some academics, who think hunting prey contributed to our bipedal stance.

Even when something has been done for millennia, it doesn’t necessitate that we keep going in the same direction. The way we eat at the dinner table has changed dramatically in the modern era. Tofu, for example, was unavailable to our ancestors, while cashew nuts were very impossible to get by in colder climates.

the option of going back after you’ve adjusted

The process of evolution and adaptation is never-ending. After weaning, animals don’t consume milk anymore. They’d get ill if they did that. They’re not stupid. In adulthood, lactase, the enzyme that animals need to break down lactose in milk, is not created. Currently, though, whole populations of people generate lactase long after stopping to consume their mother’s milk (referred to as lactase persistence).

Because they had access to more calories and other nutritional benefits, people who could eat cow (or goat) juice lived longer than those who couldn’t. To meet our energy needs, we have developed a strategy for consuming protein, vitamins, and minerals. Then, is it natural to consume milk? Do we have to stop drinking it if it isn’t safe?

In our bodies, we can see a wide spectrum of evolutionary transitions, from a move to meat millions of years ago to microbiome adjustments when humans began consuming wheat and barley. We are now a jumble of benefits and perks that have kept us afloat throughout the years.

Homo erectus, Neanderthals (who may have eaten more plants than is typically assumed), Australopithecus, the first primates (about 50–55 million years ago), or anything in-between, if we declare we wish to eat like our ancestors?

It is clear from the previous paragraphs that we should only consume meat if it is beneficial to us at this time. What matters most is how it affects our bodies in the here and now.

However, neuroimaging studies on the aging population have shown an inverse relationship between vitamin B12 and total brain volume loss over 60 years of age. A longitudinal study comprising 146 older adults (>65 years) found that the Mediterranean diet was significantly associated with preserved white matter volume, along with the reduced occurrence of depression. Moreover, a voxel-based morphometric study (based on 32 community-dwelling adults) on vitamin B6 and B12 has shown that adults with higher vitamin B6 intake had increased gray matter volume along the medial wall, anterior cingulate cortex, medial parietal cortex, middle temporal gyrus, and superior frontal gyrus, and adults with higher vitamin B12 intake had greater volume in the left and right superior parietal sulcus (3). This suggests that vegetarian and vegan diets, when they are deficient in these vitamins, may influence the brain size and brain health. 

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In this brief guide, we answered the query, “Is human vegetarian by nature?” and discussed human evolution from herbivore to omnivore.


  1. Kerna, N. A., et al. The Truth: Are Humans Vegetarian, Carnivore, or Omnivore? A Review Based on the Anatomy and Physiology of the Human Digestive Tract. EC Nutr, 2021, 16, 78-86.
  2. Luca F, Perry GH, Di Rienzo A. Evolutionary adaptations to dietary changes. Annu Rev Nutr. 2010, 30, 291-314. 
  3. Berkins S, Schiöth HB, Rukh G. Depression and Vegetarians: Association between Dietary Vitamin B6, B12 and Folate Intake and Global and Subcortical Brain Volumes. Nutrients, 2021 13, 1790.