Most people on the planet do it. But are humans even meant to eat meat? Here’s the science
By Jody McCutcheon
In our quest for the ideal diet, many of us tend to look back at the culinary habits of our earliest ancestors. Revisiting proto-humans and their preferred victuals may be a way of cutting through all the hype over today’s latest superfoods and fad diets to see what kinds of foods truly optimize human health.
But there’s no clear consensus on what our ancestors ate. Some say they were strictly vegan, while others suggest animal products were a big part of their diet.
So, are humans meant to eat meat? Presently there’s no way to know for sure. But some anthropological clues can help us arrive at a well-educated guess.
Meat Eating & Human Anatomy
The first clue is our bodies. From the structure of our mouth and teeth to our dexterous hands and our long gastrointestinal tract, our evolved anatomy suggests an herbivorous diet.
For example, our facial musculature serves two purposes: to form expressions and to chew. Our jaw’s forward-backward and side-to-side mandibular movements allow us to crush and grind plant matter, while our flat-bottomed incisors and molars were made to flatten and grind food.
Our close-set teeth also suggest we were meant to eat a plant-based diet. Carnivores’ teeth are separated by spaces, so gristle doesn’t get caught between them. That’s not the case for us, or our primate cousins.
Rather than sharp claws with which to seize prey, our hands are ideal for grabbing, planting and picking fruit and veggies.
We also have very long, herbivore-like intestines for thoroughly digesting tough-to-process plant material.
Carnivores, by contrast, have short intestinal tracts, often less than half the size of a herbivore’s intestines. That’s to quickly eliminate any swallowed flesh that would otherwise rot in their systems. These animals also have more concentrated acids in their stomach. In fact, the digestive systems of some carnivorous animals has even evolved to the extent that they have a built-in mechanism to flush out toxic meat.
As measured by our anatomical makeup then, our ancestors seem to have shared a vegetarian diet with their own ancestors: great apes and other primates.
Perhaps an occasional meat treat was thrown in for good measure. Who knows? But what’s clear is this: our bodies were not made to be carnivorous.
Meat = Bigger Brains?
At some point in human development, our brains when through a growth spurt. Some scientists say this would have been “biologically implausible” on a raw, vegan diet.
How so? Assuming that larger bodies generally possess larger brains, one study from 2012 examined the dietary habits of gorillas, which are three times as big as humans. Yet their brains have only a third of the neurons we have. This neuronal paucity was attributed to a largely vegan diet lacking in animal protein. Adding neurons to primate brains would have a fixed cost of about six calories per billion neurons.
To consume sufficient calories to support their mass, gorillas spend as much as eighty percent of daylight hours eating. But to evolve human-like brains, they’d need an extra 733 calories. That’s 2 additional hours of feeding per day.
Similarly, it is believed by some that early humans on a vegan diet would have had to eat for nine hours a day to get enough calories and nutrients for their brains to develop to such an extent.
Of course, the theory that meat-eating led to bigger human brains has its detractors. For example, it’s been argued that if gaining further neurons is only a question of consuming more calories, then humans in nut-rich areas would have profited from faster brain growth. That’s because ounce for ounce, nuts are about double the calories of red meat.
The truth is, no one really knows for sure what caused the growth spurt in our brains.
The History Of Meat Eating
If our bodies are clearly not made to be carnivorous, what caused meat eating in the first place?
The short answer is: starvation.
Some scientists claim that between 2.6 and 2.5 million years ago, the Earth got significantly hotter and drier. Previously, our human ancestors—collectively known as hominins—were subsisting mostly on fruits, leaves, seeds, flowers, bark and tubers. As the temperature rose, forests shrank and great grasslands thrived. As green plants became scarcer, evolutionary pressure forced early humans to find new sources of energy.
The grassland savannas that spread across Africa supported growing numbers of grazing herbivores. Meat became more readily available than vegetable matter at that time. The same was true for our ancestors in colder climates. There was more fauna than flora – so they ate it. In this regard, meat eating can be seen as an adaptive behaviour.
But if humans are not meant to eat meat, how did we suddenly start to digest stuff not suited towards our bodies?
Change By Fire
Again, there’s a short answer to the question above. Fire!
Cooking makes meat more digestible, releases more nutrients and calories from it, and makes it easier to chew.
Anthropologists are unsure exactly when the practice of cooking food began. Some suspect that due to changes in hominid tooth size, the earliest kitchen session may have occurred almost two million years ago. Yet any evidence of fire pits (i.e., controlled fires) is lacking.
More conservative estimates put cooking’s beginnings some time between 800,000 years ago (before our brain’s growth spurt) and 250,000 years ago (once the growth spurt was basically finished). So whether cooking (presumably vegan foods like tubers, legumes and roots) was a contributor to our brain’s growth is still unclear.
Which Is The Healthier Diet?
Meat might have contributed to brain growth and development in the past. But in the present, it certainly remains a distant second behind veggie and vegan diets on the health scale.
For example, heart disease causes more deaths per year, not only in the U.S., but in all developed countries. Much evidence suggests that a plant based diet is responsible for a significantly lower risk of heart disease and all cardiac diseases in vegan and vegetarian individuals.
A 2013 study from the University of Oxford found that vegetarians have a 32 percent lower risk of hospitalization from cardiovascular disease compared to meat and fish eaters. An analysis of 45,000 volunteers, of whom 34 percent were vegetarian, took into consideration factors such as smoking, diet, exercise and alcohol consumption.
The conclusions, published in the American Journal of Clinical Nutrition, suggested the lower blood pressure and cholesterol levels in the vegetarians contributed to their reduced risk of heart disease compared to the non-vegetarians.
Another study, published in the Journal of Academy of Nutrition and Dietetics, confirms that vegetarian diets are nutritionally optimal for all people, including pregnant women, infants and athletes. The 2016 study reported that plant-based diets are associated with a reduced risk of health conditions, including hypertension, heart disease, Type 2 diabetes, certain cancers and obesity.
Furthermore, it’s a fact that billions of humans around the globe are lactose intolerant. This suggests that our bodies haven’t fully adapted to the digestion of animal products.
If that’s not bad enough, eating meat causes us most of us to have:
- decreased energy levels
- a need to sleep more
- a higher risk of obesity and diabetes
- an increased risk of certain kinds of cancers, such as colon or prostate
On the other hand, due to a lack of B12 in soils depleted by industrial agriculture, today’s vegetarians may be deficient in vitamins B12 and retinal. Some studies show that vegetarians may have increased risk of some cancers. However, this is possibly linked to pesticides used by modern farmers, rather than a plant based diet itself.
So, are humans meant to eat meat?
It seems that human bodies were not originally made to eat meat. And given the myriad serious health issues associated with meat eating, it’s probably wise to cut back on the stuff, at the very least.
Nutrition and diets aside, many of us also feel that shunning meat is a moral choice now. Not only for saving the lives of animals, but for preserving the life of the very planet we live on.
“Nothing will benefit human health and increase the chances for survival of life on earth as much as the evolution to a vegetarian diet.”
What do you think? Are humans meant to eat meat? Let us know in the comments, below!