Some people are highly squeamish about eating sushi. Others like their steaks well done and cringe at the idea of eating it rare.
Today, with a seemingly limitless array of food options, most of our foods that include meat are cooked. When you compare our species’ eating habits with those of every other animal on Earth, we are the only ones who cook fresh food. It’s almost baffling to realize that the overwhelming majority of us have been socially conditioned to seek out meat that is fresh and then cook it before we eat it.
To understand how we became the eaters we are today, thriving on everything from beef jerky and roast chicken, to kale chips and grilled veggies, we have to look back a couple million years or so.
Homo erectus, Hominid of Fire
Most people forget that humans have evolved from ugly, ape-like primates (and some even deny it, but that’s a separate story, of course). As long as 2.3 million years ago, the first “true human” – Homo habilis – appeared. H. habilis was four to five feet tall and weighed anywhere from 40 to 100 pounds.
As far as appearance goes, H. habilis looked like your typical caveman – or a cross between an ape and the modern human species that we are today (Homo sapiens). Although plants made up the majority of his diet, he definitely ate flesh, either by scavenging around for it or by hunting it himself.
About 500,000 years later, or 1.8 million years ago, H. habilis evolved into a substantially more advanced species called Homo erectus. H. erectus was taller at 5 to 6 feet, with a brain up to twice the size of the prior species. It wasn’t anywhere near as large or as developed as today’s human brains, but the difference in brain size between H. habilis and H. erectus was quite significant.
For decades, archeologists struggled to pinpoint exactly when hominids started cooking with fire, but a recent discovery from a cave in South Africa documented the remains of campfires from a million years ago. That’s 200,000 years earlier than any other previously discovered evidence of hominid-made fire.
Unlocking the Power of Excess Food Energy
Cooked food not only tastes better, it’s easier to chew and digest. A team of Harvard University researchers who studied the tooth sizes and body masses of four extinct hominids, as well as those of modern day humans, found that H. erectus spent about 6.1 percent of his time during an average day eating. In contrast, his predecessor H. habilis spent about 7.2 percent of his day on feeding, while we modern humans are at about 4.7 percent.
H. erectus had evolved because he was spending less time and energy on chewing and digesting food, and this led to dramatic changes in tooth size, as well as smaller intestines. Cooked food was easier to chew, and enabled him to absorb more nutrients, resulting in more calories to enjoy and fewer calories needed for digestion.
Richard Wrangham, author of Catching Fire: How Cooking Made Us Human, says that the power of the flame resulted in the dramatic evolutionary transformation between H. habilis and H. erectus. With more calories available, the species’ energy-hungry brain was able to harness that excess energy, which was used to grow a larger cranium.
Literally Food for Thought
The human brain is one of the most calorie-hungry organs in the body. At rest, the body designates around one-fifth of the calories consumed to powering the brain and its more than 100 million cells – even if it’s not thinking or working hard at all.
When you cook a piece of meat, collagen – the meat’s connective tissue – breaks down. Likewise, when you cook plants, the cell walls are softened so they can more easily release stores of starch and fat.
The brain’s hunger for more energy and a reduced need for a more powerful digestive system is why Wrangham gives fire the credit for altering the anatomy of H. erectus, and essentially leading us to develop into the advanced species of hominid we are today. No other primate has as many brain neurons than humans. On a raw food diet, which takes more energy to chew and digest, it’s a lot harder to consume enough calories to sustain and grow a large brain.
You are what You Eat
Given the evidence that the H. erectus learned how to cook, grew a bigger brain, and shrank his digestive system, it seems convincing enough that humans certainly did evolve to eat cooked food – meat, in particular. But vegetarians, vegans, raw food advocates, and countless other nutrition experts would likely be clever enough to argue otherwise.
Whether you suck down green smoothies every day or roast entire chickens covered in layers of bacon, one thing is definitely clear. We all may belong to the same species, but these days, it’s personal genetics, how we’re raised, cultural norms, values, level of income, and taste preference that tend to influence our food choices, rather than a quest for survival.