The Natural Human Diet
When you see dead animals on the side of the road, are you tempted to stop and snack on them? Does the sight of a dead bird make you salivate? Do you daydream about killing cows with your bare hands and eating them raw? If you answered no to these questions, congratulations—like it or not, you’re an herbivore.
According to biologists and anthropologists who study our anatomy and our evolutionary history, humans are herbivores who are not well suited to eating meat. Humans lack both the physical characteristics of carnivores and the instinct that drives them to kill animals and devour their raw carcasses.
Although many humans choose to eat a wide variety of plant and animal foods, earning us the dubious title of “omnivore,” we’re anatomically herbivorous.
Teeth, Jaws, and Nails
Humans have short, soft fingernails and pathetically small “canine” teeth. In contrast, carnivores all have sharp claws and large canine teeth that are capable of tearing flesh.
Carnivores’ jaws move only up and down, requiring them to tear chunks of flesh from their prey and swallow them whole. Humans and other herbivores can move their jaws up and down and from side to side, allowing them to grind up fruit and vegetables with their back teeth. Like other herbivores’ teeth, humans’ back molars are flat for grinding fibrous plant foods. Carnivores lack these flat molars.
Dr. Richard Leakey, a renowned anthropologist, summarizes, “You can’t tear flesh by hand, you can’t tear hide by hand. Our anterior teeth are not suited for tearing flesh or hide. We don’t have large canine teeth, and we wouldn’t have been able to deal with food sources that require those large canines.”
Carnivores swallow their food whole, relying on their extremely acidic stomach juices to break down flesh and kill the dangerous bacteria in meat that would otherwise sicken or kill them. Our stomach acids are much weaker in comparison because strong acids aren’t needed to digest pre-chewed fruits and vegetables.
Carnivores have short intestinal tracts and colons that allow meat to pass through the animal relatively quickly, before it can rot and cause illness. Humans’ intestinal tracts are much longer than those of carnivores of comparable size. Longer intestines allow the body more time to break down fiber and absorb the nutrients from plant-based foods, but they make it dangerous for humans to eat meat. The bacteria in meat have extra time to multiply during the long trip through the digestive system, increasing the risk of food poisoning. Meat actually begins to rot while it makes its way through human intestines, which increases the risk of colon cancer.
Read author John Robbins’ discussion of the anatomical differences between humans and carnivores or review Dr. Milton Mills’ entire article on the topic to learn more.
Humans also lack the instinct that drives carnivores to kill animals and devour their raw carcasses. While carnivores take pleasure in killing animals and eating their raw flesh, any human who killed an animal with his or her bare hands and ate the raw corpse would be considered deranged. Carnivorous animals are excited by the scent of blood and the thrill of the chase. Most humans, on the other hand, are revolted by the sight of blood, intestines, and raw flesh and cannot tolerate hearing the screams of animals being ripped apart and killed. The bloody reality of eating animals is innately repulsive to us, another indication that we weren’t designed to eat meat.
If We Were Meant to Eat Meat, Why Is It Killing Us?
Carnivorous animals in the wild virtually never suffer from heart disease, cancer, diabetes, strokes, or obesity, ailments that are caused in humans in large part by the consumption of the saturated fat and cholesterol found in meat.
Fat and Cholesterol
Studies have shown that even when fed 200 times the amount of animal fat and cholesterol that the average human consumes each day, carnivores do not develop the hardening of the arteries that leads to heart disease and strokes in humans.
Human bodies, on the other hand, weren’t designed to process animal flesh, so all the excess fat and cholesterol from a meat-based diet makes us sick. Heart disease, for example, is the number one killer in the U.S., according to the American Heart Association, and medical experts agree that this ailment is largely the result of the consumption of animal products. Meat-eaters have a 32 percent higher risk of developing heart disease than vegetarians do!
We consume twice as much protein as we need when we eat a meat-based diet, and this contributes to osteoporosis and kidney stones. According to peer-reviewed studies, animal protein raises the acid level in our blood, causing calcium to be excreted from the bones in order to restore the blood’s natural pH balance. This calcium depletion leads to osteoporosis, and the excreted calcium ends up in the kidneys, where it can form kidney stones or even trigger kidney disease.
Consuming animal protein has also been linked to cancer of the colon, breast, prostate, and pancreas. According to nutrition expert T. Colin Campbell, the director of the Cornell-China-Oxford Project on Nutrition, Health, and Environment, “In the next ten years, one of the things you’re bound to hear is that animal protein … is one of the most toxic nutrients of all that can be considered.”
Eating meat can also have negative consequences for stamina and sexual potency. One Danish study indicated that “[m]en peddling on a stationary bicycle until muscle failure lasted an average of 114 minutes on a mixed meat and vegetable diet, 57 minutes on a high-meat diet, and a whopping 167 minutes on a strict vegetarian diet.” Besides having increased physical endurance, vegan men are also less likely to suffer from impotence.
Since we don’t have strong stomach acids like carnivores to kill all the bacteria in meat, dining on animal flesh can also give us food poisoning. According to the U.S. Department of Agriculture, meat is a significant cause of foodborne illnesses in the U.S. because it’s often contaminated with dangerous bacteria such as E. coli, listeria, and campylobacter. Every year in the U.S. alone, food poisoning sickens more than 48 million people and kills more than 3,000.
Dr. William C. Roberts, editor of the authoritative American Journal of Cardiology, sums it up this way: “[A]lthough we think we are one and we act as if we are one, human beings are not natural carnivores. When we kill animals to eat them, they end up killing us because their flesh, which contains cholesterol and saturated fat, was never intended for human beings, who are natural herbivores.” Learn more about how meat damages human health.
Human Evolution and the Rise of Meat-Heavy Diets
If it’s so unhealthy and unnatural for humans to eat meat, why did our ancestors sometimes turn to flesh for sustenance?
During most of our evolutionary history, we were largely vegetarian: Plant foods, such as yams, made up the bulk of our ancestors’ diet. The more frequent addition of modest amounts of meat to the early human diet came with the discovery of fire, which allowed us to lower the risk of being sickened or killed by parasites in meat. This practice didn’t turn our ancestors into carnivores but rather allowed early humans to survive during periods in which plant foods were unavailable.
Until recently, only the wealthiest people could afford to feed, raise, and slaughter animals for meat, and less wealthy and poor people ate mostly plant foods. Consequently, prior to the 20th century, only the rich were plagued routinely with diseases such as heart disease and obesity.
Since 1950, the per capita consumption of meat has almost doubled. Now that animal flesh has become relatively cheap and is easily available (thanks to the cruel, cost-cutting practices of factory farming), deadly ailments such as heart disease, strokes, cancer, and obesity have spread to people across the socio-economic spectrum. And as the Western lifestyle spills over into less developed areas in Asia and Africa, people there, too, have begun to suffer and die from diseases associated with meat-based diets.