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 protohumans 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.
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).
Rather than sharp claws with which to seize prey, we possess hands that 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) to quickly eliminate any swallowed flesh that would otherwise rot in their system. Our guts can process many different types of foods, from the more difficult ones, like grains and legumes, to easier-to-digest berries and nuts
As measured strictly by anatomical makeup then, our earliest ancestors seem to have shared a vegetarian diet with their own ancestors: the great apes and other primates. Perhaps an occasional meat treat was thrown in for good measure. Or did animal flesh play a more prominent role in their diet?
According to several studies done in the last few years, the growth spurt experienced by the proto-human brain that occurred over the span of a few million years would have been “biologically implausible” on a raw, vegan diet. 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. Researchers at the Federal University of Rio de Janeiro found, however, that despite their larger size, gorillas have only a third of the neurons that humans do. This neuronal paucity was attributed to a largely vegan diet lacking in animal protein, and 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–or two additional hours of feeding–per day. Similarly, 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–an unlikely occurrence, given the dangers and other difficulties of gathering so much food. So what caused the accelerated growth?
Research suggests that the human diet changed about 2.3 million years ago to accommodate meat. That’s when cut marks from sharp tools began to appear on animal bones, suggesting humans had begun hunting and using tools to cut meat. Humans probably began eating meat for at least a couple different reasons: one is a significant decline in the quality of plant foods, as receding forests left them with fewer nutritious leaves and fruits to consume -meat indisputably delivers a sufficient cocktail of calories, proteins, fat, vitamins (including B12), minerals and essential amino acids to facilitate brain growth and maintenance, thus allowing us to survive even in the absence of an abundance of plant foods. A second is climate change, as meat is more readily available than vegetable matter in colder climates. In this regard, meat eating can be seen as an adaptive behaviour.
So while early humans obviously didn’t start eating it for the purpose of making their brains bigger, it may have been one of the consequences. 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, as ounce for ounce nuts are about double the calories of red meat.
Researchers also argue that another method of increasing food’s caloric and nutrient value–thereby accelerating brain growth–is by cooking it. Cooking makes food more edible year-round, releases more nutrients and calories from meats and vegetables and makes both easier to chew and digest. Chewing breaks up food, which exposes more surface area from which the gut can absorb nutrients. More calories are available per serving, while the gut spends less time digesting them. Starchy foods like potatoes are especially softened by cooking. And you needn’t chew your food as much if it’s cooked, thereby conserving energy.
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.
Meat may 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. In general, due to all the cholesterol and saturated fat in animal products, meat eaters tend to experience more health problems than do non-meat eaters, including heart disease, cancer and diabetes, suggesting that our bodies haven’t fully adapted to eating meat. If that’s not bad enough, eating meat causes us to experience decreased energy levels, a need to sleep and an increased risk of obesity. Cutting right to the gristle, red meat consumption is linked to a shorter lifespan.
So just because evidence suggests our earliest ancestors may have benefitted from cooking and eating meat doesn’t mean we should eat it today. Conversely, surviving and thriving back then on a vegan diet may not have been possible, but with our accumulated knowledge of various foods and balanced diets, it definitely is today.
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. A vegetarian himself, Albert Einstein argued that “Nothing will benefit human health and increase the chances for survival of life on earth as much as the evolution to a vegetarian diet.”