Evidence of the diets of ancient humans can be found in our anatomy and our closest evolutionary cousins.
There has been fierce debate over which foods humans ate prior to the invention of agriculture. The result is strong evidence suggesting that our ancestors subsisted primarily on plant-based foods.
Humans are part of the ape family, including chimpanzees, gorillas, and orangutans, and our digestive systems closely resemble theirs. Apes are primarily frugivores (fruit-eating), and though they may supplement with insects and bird eggs, they rarely eat meat. From this starting point, humans have adapted their societies around the foods they were easily able to obtain and consume, most often plant-based foods unique to a region. This is especially clear in the introduction of agriculture, with humans having adapted differently in different regions based on what they were growing and consuming in large quantities. Yet the common thread running through all of this history is that—with few exceptions— the human diet has likely been primarily made up of plant-based foods such as fruits, leaves, seeds and nuts.
Human bodies display certain characteristics that suggest that our diet should consist primarily of plants and plant-based foods. These include the formation of our teeth, the way our jaw moves, the form of our lips, and even the shape of our digestive tract. Dr. Milton R. Mills lays out the anatomical and physiological evidence that humans have evolved to consume a mostly plant-based diet in his essay “The Comparative Anatomy of Eating.”
In his essay, Dr. Mills notes that not only are human teeth better adapted to a herbivorous diet but so is the entire mouth. Like other herbivores, our teeth are close together and flat, perfect for use on soft materials such as fruits. Even our elongated canines can be found in other apes, who use them primarily for display or defense. This contrasts with the teeth of carnivores which are spaced more widely apart and are more blade-like—ideal for shredding and tearing.
When considering the mouth in its entirety, humans also display other similarities to herbivores. Such markers include fleshy lips and a smaller mouth opening, very different from the hinge-like jaws of a cat or other carnivore. Our jaws are also able to move more freely than a carnivore’s, as we are able to move them both up and down and side to side, giving us greater use of our incisors while allowing us to crush and grind our food.
As with the rest of our gastrointestinal tract, our teeth are not predisposed to meat consumption. This was recognized by researchers as long ago as the mid-nineteenth century, and it continues to be supported by more up-to-date anatomical and physiological evidence. Most notably, our physical predisposition toward plant-based foods can be seen in the types of teeth we have. Our mouth is full of incisors and molars that are similar to those of other herbivores. Our incisors, like those of herbivores, are broad, flattened and shaped like a spade and our molars are flattened with nodular cusps, another trait common among other herbivores. As for our canines, they are short and blunted, very different from the long and sharp canines of carnivores, and more similar to the teeth of herbivores.
Anyone following a plant-based diet will be well acquainted with having their diet second-guessed by family members, friends, and even strangers that claim to be concerned about nutritional deficiency. However, as the 79 million vegans around the world can attest, eating plant-based can easily fulfill all your nutritional needs. In fact, following a plant-based diet has been associated with a range of health benefits when compared to more meat-heavy food preferences.
Although there are nutrients like vitamin B12 that are important to supplement with if one is following a plant-based diet, a University of Oxford study found that, on average, people who eat meat have more nutritional deficiencies than people who don’t eat meat.
There are several reasons why humans should think twice before selecting a steak at the supermarket for a fancy dinner or a burger at a fast-food chain for a quick bite. Everything from red meats being classified as carcinogenic to food poisoning affecting one in six Americans every year suggests that we would be better served by choosing plant-based meals, especially those composed primarily of whole foods such as fresh, frozen, or canned vegetables and fruits, nuts, and whole grains.
Eating a plant-based diet has been tied to improved heart health in a number of studies. One such study published in The Journal of the American College of Cardiology tracked the heart health of 16,000 participants over several years. At the conclusion of the study period, researchers found that those that followed a plant-based diet had a 41 percent lower risk of heart failure than those in the other diet groups. On the other hand, participants that followed a diet consisting of processed meats, organ meats, eggs, and highly processed foods were at a 72% higher risk of heart failure.
An astonishing 7.69 percent of people worldwide (600 million) fall ill with food poisoning every year. Before the COVID-19 pandemic, deaths due to food poisoning accounted for 7.5 percent (420,000) of all deaths globally. The most common type of food poisoning is campylobacteriosis, or Salmonella, which is usually contracted by consuming meats that have not been properly cooked or raw, unpasteurized dairy. As with most strains of food poisoning, the symptoms include diarrhea, vomiting, and cramping. Symptoms typically last three to six days and begin two to five days following exposure.
Our digestive system has evolved to look more similar to those of herbivores than those of carnivores or even omnivores. This is a point discussed in Dr. Milton R. Mills' paper arguing for our physiological predisposition to a plant-based diet. One significant difference between us and carnivores is that our small intestine is very long, averaging 10 to 11 times our body length, while that of carnivores is much shorter, typically five or six times the body length. Our longer intestines allow our organs the time necessary to break down the fibrous plant-based foods we eat. A carnivore’s larger stomach to small intestine ratio means food spends longer in the stomach, allowing carnivores to consume a large amount at once that they then digest more slowly, and allowing them to survive longer between meals. Carnivores’ stomachs also produce significant amounts of hydrochloric acid, which aids in breaking down protein and killing potentially dangerous bacteria found in decaying animal flesh.
Unlike certain bats and other animals that have adapted to consuming large amounts of blood, our bodies are unable to handle the substance. This is particularly due to the high level of iron in blood which, if too much is consumed, can cause various conditions including liver damage, fluid buildup in the lungs, and even death.
Although many people are concerned about getting enough protein, eating too much protein can actually have serious health repercussions for humans. The overconsumption of protein is especially common in industrialized countries where having meat and dairy products with every meal is commonplace, with these foods providing well above the recommended 15 percent of calories from protein. Most Americans consume more than double the amount of daily recommended protein. High levels of protein intake has been associated with cancer, kidney stones, obesity, and coronary heart disease.
What Are Humans Supposed To Eat Naturally?
Our anatomy and physiology have evolved to resemble herbivores more than carnivores or even most omnivores. The resemblance between us and other species that primarily consume plants can be seen in everything from the fleshy nature of our lips and the chemical makeup of our saliva to our lengthy small intestine and the joints of our jaws. This indicates that we are best suited to a diet made up mostly of plant foods, a diet that has been followed for generations by cultures and individuals around the world. The human ability to thrive on these diets and even reduce the likelihood, and sometimes even reverse the onset, of many diseases including heart disease and diabetes has been documented repeatedly.
An anthropological, physiological, and anatomical look at humans and our bodies reveals that we may be best suited to consuming a plant-based whole food diet. Our jaw structure, teeth, short intestine, the chemicals in our guts, and how our bodies deal with protein all suggest this to be the case.
Getting started on a plant-based whole-food diet can be daunting. If you’re interested in starting to shift in that direction, there are many fantastic resources available online to help you gradually reduce your consumption of animal products while increasing the whole grains, vegetables, fruits, and nuts you eat. Starting with simple swaps, like plant-based milk in your cereal or beans in your tacos, is a great way to start exploring other options. There are also delicious plant-based alternatives to beef, cheese, and other animal products that can make transitioning even easier.