Are Humans Carnivores by Nature?

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Are Humans Carnivores by Nature?

As a vegan you often hear that we humans have always eaten meat and that we are carnivores or at least omnivores by nature. For a long time, animal products have been regarded as a central component of our diet since primeval times.

However, researchers have found out that our food has always been strongly plant-based. This is indicated by many anatomical and physiological characteristics. So, are we humans anatomically more like a natural carnivore or a natural herbivore?

In order to clarify this, we take a closer look at the anatomy of the different types of nutrition. In addition, we compare the characteristics of carnivores, omnivores, herbivores and frugivores to those of us humans.

Comparison of the Different Forms of Diet

TypeExample
Diet
Carnivores
(meat eaters)
Lions, wolves, cats, birds of prey, crocodiles Meat
Omnivores Dogs, bears, wild boars, ratsMeat, vegetables, fruits and parts of plants
Herbivores
(plant eaters)
Horses, cattle, goats, sheepPlants, leaves, grasses and herbs
Frugivores
(fruit eaters)
Monkeys, elephants, many birds Fruits, vegetables, plants, nuts, sometimes insects

As can be seen in this table, there are 4 different types of diets. But which one of these types is closest to us humans?

Behavior

Instincts
SpeedEndurance Sleep
Carnivores Strong hunting instinct,
strong killing instinct
Very high top speed
e. g. Cheetah 90-120 km/h
Very low enduranceSleep up to
18 hours a day
OmnivoresHunting instinct,
killing instinct
High top speed
e. g. dogs 50-80 km/h
Average endurance Sleep up to
12-14 hours a day
Herbivores No hunting instinct,
flight instinct
Medium top speed
e. g. horse 50-60 km/h
Very high enduranceSleep only
a few hours or
snooze rather than sleep
Frugivores No hunting instinct,
flight instinct
Low top speed
e. g. monkey approx. 40 km/h
Average enduranceSleep
4-12 hours a day
HumansNo hunting instinct,
flight instinct
Low top speed
Humans approx. 30-40 km/h
Average endurance Sleeping
6-9 hours a day

As you can see, carnivores and omnivores have a strong hunting instinct. In addition, they are able to reach very high speeds to catch their prey. Also, carnivores possess long claws to hold on to their prey.

If we compare that to us humans, we see that we have no hunting instinct at all. When we see a squirrel fleeing to a tree in front of us, we don’t feel the impulse to chase it. Or if we were locked in a room with a rabbit and an apple, we would eat the apple first and not the rabbit. How could we? We couldn’t even kill it without tools. Our fingernails and teeth are not suitable in any way to tear apart an animal.

comparison of claws

Another example of our lack of carnivorous instincts: If we accidentally hit a deer with our car, we don’t salivate when we see the dead animal. Why not? The organs and entrails are the first things carnivores eat after killing a prey. If we were a natural meat eater, the sight of the torn organs should attract us, not repel us.

Teeth

FangsIncisors Molars
Carnivores Long sharp fangsShort and pointed incisors Blade-shaped molars
OmnivoresLong sharp fangsShort and pointed incisors Blade shaped / Crushing molars
Herbivores Underdeveloped, blunt fangs Large, flattened incisorsFlat and strong molars
FrugivoresReißzähne zur Verteidigung Large, flattened incisorsFlat molars
HumansUnderdeveloped, blunt fangs Large, flattened incisorsFlat molars

All teeth of carnivorous animals are long, sharp and pointed. They serve to tear out the raw meat. The molars of herbivores, fruit-eaters and humans, on the other hand, are blunt. For they are intended for the crushing and grinding of food. It is very difficult for us to cut tendons or muscles with our teeth.

comparison of claws

Another aspect of food intake is the tongue. The tongue of a carnivore is as rough as sandpaper. Anyone who’s ever been licked by a cat knows that. This allows carnivores to scrape off meat fibres and tendons from bones or cartilage with their tongue. In contrast, the human tongue is relatively smooth.

Movement of Jaw and Eating Behaviour

Jaw
Jaw MovementEating Behaviour
Carnivores
Lower jaw sits inside the upper jaw Only up and down movement
No lateral or forward movement possible
Tearing, gobbling,
swallowing without chewing
OmnivoresLower jaw sits inside the upper jaw Only up and down movement
No lateral or forward movement possible
Tearing, gobbling or swallowing
Crushing/squashing of food
HerbivoresLower jaw connects to the underside of the upper jaw Large lateral as well as forward and backward movements to grind the foodNo tearing,
chew a lot
Frugivores Lower jaw connects to the underside of the upper jaw Large lateral as well as forward and backward movements to grind the food No tearing,
chew their food
HumansLower jaw connects to the underside of the upper jaw Large lateral as well as forward and backward movements to grind the foodNo tearing,
chew their food

The jaws of carnivores and omnivores only move up and down. That’s because they rip out their food and gobble it down. The jaws of herbivores, frugivores and humans, on the other hand, can also move sideways. Because we chew our food before we swallow it.

Saliva and Urine

Salivary Glands             Type of Saliva Sweat Glands
Carnivores Small salivary glands Acid saliva to digest animal protein without the starch-degrading enzyme ptyalin Sweat glands only in the paws, panting to cool the blood
Possess no pores
OmnivoresSmall salivary glands Acid saliva to digest animal protein without the starch-degrading enzyme ptyalin Depending on species
sweat glands only in the paws or on the whole body
Possess no pores
Herbivores Big salivary glands Alkaline saliva with the starch-degrading enzyme ptyalinSweat glands all over the body
Possess pores
Frugivore Big salivary glands Alkaline saliva with the starch-degrading enzyme ptyalin Sweat glands all over the body
Possess pores
HumansBig salivary glands Alkaline saliva with the starch-degrading enzyme ptyalinSweat glands all over the body
Possess pores

The saliva of a carnivores and omnivores is acidic and therefore ideal for splitting animal protein. The saliva of herbivores, frugivores and humans, on the other hand, is usually alkaline. It also contains ptyalin and amylase to digest carbohydrates.

However, many people today have an acid saliva, because today’s usual diet with lots of meat and dairy products leads to an acid metabolism situation. Plant based foods, especially with fresh vegetables, have a significant base surplus.

Carnivores can hardly sweat because they have no skin pores. Instead, they dissipate excess body heat through the tongue by panting. Humans, on the other hand, sweat with their skin and possess sweat pores, just like herbivores and frugivores.

Stomach and Urinary System

Stomach
KidneysUrine           
Carnivores Simple round sac with high amount of strong hydrochloric acid to digest tough animal muscles, bones etc.Form uricase,
are able to cope with ten to fifteen times more uric acid
Acid urine
Omnivores Simple round sac with high amount of strong hydrochloric acid to digest tough animal muscles, bones etc. Form uricase,
are able to cope with ten to fifteen times more uric acid
Acid urine
Herbivores Elongated shape, complex structure; little hydrochloric acid and pepsineDon’t form uricase,
only uric acid formed by the body itself can be degraded
Mostly alkaline urine
Frugivores Elongated shape, complex structure; little hydrochloric acid and pepsineDon’t form uricase Mostly alkaline urine
HumansElongated shape, complex structure; little hydrochloric acid and pepsineDon’t form uricase Mostly alkaline urine

The stomach of a carnivores produces ten times more hydrochloric acid than that of a herbivore or a human. It has the form of a simple bag, whereas the stomach of a pure herbivore has an elongated shape and a complicated, furrowed structure. On the other hand, we humans have a stomach that is very similar to that of frugivores.

The kidneys, liver and spleen of carnivores and omnivores produce uricase. This allows them to detoxify ten to fifteen times more uric acid than herbivores, frugivores or humans can. Because meat and entrails contain a lot of uric acid. In contrast, plants (with the exception of cereals, coffee and cocoa) contain practically no uric acid. Nevertheless, the uric acid level in the blood of humans rises strongly due to a meat-rich diet. Too much uric acid, however, favours gout, heart and blood vessel diseases.

The urine of a carnivore is sour at any time of the day. The urine of herbivores, frugivores and humans, on the other hand, is only sour in the morning and normally alkaline for the rest of the day. But as just mentioned, many people are over acidified by a meat heavy diet and therefore have the acid urine of a carnivore.

Cholesterol and Vitamins

Cholesterol and
Vitamin A
Vitamin C
CarnivoresMetabolize high amounts of cholesterol and vitamin ABody produces vitamin C itself
OmnivoresMetabolize high amounts of cholesterol and vitamin ABody produces vitamin C itself
Herbivores Metabolize only small amounts of cholesterol and vitamin ABody produces vitamin C itself
Frugivores Metabolize only small amounts of cholesterol and vitamin ADaily intake of vitamin C via food (fruits) necessary
HumansMetabolize only small amounts of cholesterol and vitamin ADaily intake of vitamin C via food (fruits) necessary

The human body is not capable of producing vitamin C itself. The only creatures that cannot do this are guinea pigs and monkeys. Because during their evolution these species have always eaten fresh vegetables and fruits, which contain an excess of vitamin C in their raw state.

Meat, on the other hand, contains vitamin C only in small, insufficient traces. That’s why carnivores have to be able to produce it themselves. But pure herbivores can also produce vitamin C themselves.

Intestine

Intestinal length Intestinal movement Colon Duration of Digestion      
Carnivores 1.5 – 3 times as long as body length Does not require fiber to stimulate bowel movementShort, smooth structure and alkaline2 – 4 hrs
Omnivores3 times as long as body length Does not require fiber to stimulate bowel movement Short, smooth structure and alkaline 6 – 10 hrs
Herbivores 20 times as long as body length Requires fiber to stimulate bowel movement Long, looped and acidic24 – 48 hrs
Frugivores 9 – 12 times as long as body length Requires fiber to stimulate bowel movement Long, sac shaped and acidic12 – 18 hrs
Humans 9 – 12 times as long as body length Requires fiber to stimulate bowel movement Long, sac shaped and acidic12 – 18 hrs

The intestines of carnivores are only three times as long as their bodies. This short, smooth intestine ensures that the fast decomposing meat is digested quickly and leaves the body as fast as possible. Because putrefactive poisons are dangerous for all mammals.

Pure herbivores, on the other hand, have an intestinal tract almost 20 times as long as their body. They are also able to metabolize cellulose, which is a major component of plant cell walls.

Our human intestinal system and that of great apes, in contrast, is about 9 to 12 times as long as the body. Because we have a tortuous intestine with a large surface. This keeps the food in the body for as long as possible and thus makes better use of it.

Summary

As shown above, humans have virtually no characteristics of natural carnivores. But we are also no herbivores like cattle or horses. Humans are much more frugivores regarding their physical characteristics, that means we are natural fruit and vegetable eater. The anatomy of our digestive tract, the pH value and the composition of our digestive secretions are similar to those of great apes. Their natural food consists of leaves, buds, stems, fruits, seeds, nuts, roots and sometimes insects.

The fact that we eat meat is mainly due to the last ice age (75,000 – 12,000 years B. C. ). Because in this period it was impossible to cover the necessary daily food intake by vegetables and plants. Therefore people started to hunt and eat meat. Through this fat- and protein-rich food our ancestors were able to survive and defy the cold. We humans evolved in such a way that we can survive as much as possible. Deviations from the optimum diet are widely tolerated by our bodies.

Modern Lifestyle

Today, however, our survival no longer depends in any way on the consumption of animal products. On the contrary, a diet based heavily on meat can even have unhealthy consequences. Because our way of life has changed fundamentally. In the Stone Age, meat came from wild game and it was hard physical labor to hunt.

Today we only have to go to the supermarket to have access to an abundance of fresh fruit and vegetables at any time of the year. Nevertheless, most people today eat much more meat and animal products than their grandparents, for example. In addition, most of the animal products now come from factory farming and contain antibiotics and hormones. Our average life of today with very few exercise and sport is not very compatible with the energy-rich food.

A plant-based diet consisting of fruit, vegetables, legumes, nuts, kernels and seeds corresponds best to the human organism. For us humans, plant based food is not only healthier and easier to digest, but it is also better for the environment.

You may find many other interesting articles in subsections Why Vegan and Vegan Life.

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