Eating this raw diet took a lot of time and effort. So we gathered stones and bashed prey against rocks. Tenderizing food, especially meat, spared us from some of the effort of digesting and chewing, which saved energy. We used this extra energy to grow a larger brain.
Grilling food was even better. Around 800,000 years ago, we began processing food in fire, which released an enormous amount of additional calories. Our large intestines, which helped break down rough and fibrous fruits and vegetables, would shrink considerably under this new diet, and that change alone saved even more energy. These more modern ancestors, Homo erectus, used it to grow an even bigger brain—an astounding 50 percent larger than those of our habilis ancestors.
We began to look less like apes and more like people. If you could take a Homo erectus, dress him in a Brooks Brothers suit, and put him on a subway, he probably wouldn’t draw a second glance. These ancient ancestors were genetically similar enough to possibly have our children.
The innovation of mashing and cooking food, however, had consequences. The quickly growing brain needed space to stretch out, and it took it from the front of our faces, home to sinuses, mouths, and airways. Over time, muscles at the center of the face loosened, and bones in the jaw weakened and grew thinner. The face shortened and the mouth shrank, leaving behind a bony protuberance that replaced the squashed snout of our ancestors. This new feature was ours alone and distinguished us from other primates: the protruding nose.
The problem was that this smaller, vertically positioned nose was less efficient at filtering air, and it exposed us to more airborne pathogens and bacteria. The smaller sinuses and mouth also reduced space in our throats. The more we cooked, the more soft, calorie-rich food we consumed, the larger our brains grew and the tighter our airways became.
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Homo sapiens first emerged on the African savanna around 300,000 years ago. We were among a coterie of other human species: Homo heidelbergensis, a robust creature who built shelters and hunted big game in what is now Europe; Homo neanderthalensis (Neanderthals), with their massive noses and stunted limbs, who learned to make clothes and flourish in frigid environments; and Homo naledi, a throwback to early ancestors, with tiny brains, flared hips, and spindly arms that hung down from squat bodies.
What a sight it might have been, these ragtag species all gathered around a blazing campfire at night, a Star Wars cantina of early humanity, sipping river water from palm cups, picking grubs from each other’s hair, comparing the ridges of their brows, and scampering off behind boulders to have interspecies sex in the glow of starlight.
Then, no more. The big-nosed Neanderthals, the scrawny naledi, the thick-necked heidelbergensis were all killed off by disease, weather, each other, or animals, or laziness, or something else. There was only one human left in the long family tree: us.
In colder climates, our noses would grow narrower and longer to more efficiently heat up air before it entered our lungs; our skin would grow lighter to take in more sunshine for production of vitamin D. In sunny and warm environments, we adapted wider and flatter noses, which were more efficient at inhaling hot and humid air; our skin would grow darker to protect us from the sun. Along the way, the larynx would descend in the throat to accommodate another adaptation: vocal communication.
The larynx works as a valve to shuttle food into the stomach and protect us from inhaling it and other objects. Every animal, and every other Homo species, had evolved a higher larynx, located toward the top of the throat. This made sense, since a high larynx functions most efficiently, allowing the body to rid itself quickly should anything get stuck in our airways.
As humans developed speech, the larynx sank, opening up space in the back of the mouth and allowing a wider range of vocalizations and volumes. Smaller lips were easier to manipulate, and ours evolved to be thinner and less bulbous. More nimble and flexible tongues made it easier to control the nuance and structure of sounds, so the tongue slipped farther down the throat and pushed the jaw forward.
But this lowered larynx became less efficient at its original purpose. It created too much space at the back of the mouth and made early humans susceptible to choking. We could choke if we swallowed something too big, and we’d choke on smaller objects that were swallowed quickly and sloppily. Sapiens would become the only animals, and the only human species, that could easily choke on food and die.
Strangely, sadly, the same adaptations that would allow our ancestors to outwit, outmaneuver, and outlive other animals—a mastery of fire and processing food, an enormous brain, and the ability to communicate in a vast range of sounds—would obstruct our mouths and throats and make it much harder for us to breathe. This recessed growth would, much later, make us prone to choke on our own bodies when we slept: to snore.*
None of this mattered to the early humans, of course. For tens of thousands of years, our ancestors would use their wildly developed heads to breathe just fine. Armed with a nose, a voice, and a supersized brain, humans took over the world.
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I’d been thinking about our hirsute forebears ever since I’d visited Evans months back. There they were, crouched along the rocky African shore, articulating the first vowels with their flexible lips, pulling in easy breaths through gaping nasal apertures, and chomping on braised rabbit with perfect teeth.
And here I am, slack-jawed under an LED light, staring at Wikipedia’s Homo floresiensis page on my phone, chewing on bits of a low-carb nutritional bar with crooked teeth, coughing and wheezing and sucking exactly no air through my obstructed nose.
It’s evening on the second day of the Stanford mouthbreathing experiment, and I’m in bed with silicone plugs jammed inside my nasal cavities, covered with tape. For the past few nights I’ve been splayed out in a part of my house usually reserved for relatives and friends. I had a feeling that my mouthbreathing lifestyle might be a challenge for my wife. Lying here, tossing and turning, thinking about cavemen and unable to sleep, I’m happy I moved.
I’ve got a pulse oximeter device about the size of a matchbook strapped to my wrist. There’s a glowing red wire extending from it and wrapping around my middle finger. Every few seconds, the device records my heart rate and blood oxygen levels, using this information to assess how often and how severely my too-deep tongue might get lodged in my too-small mouth and cause me to hold my breath, a condition more commonly known as sleep apnea.
To gauge the severity of my snoring and apnea, I’ve downloaded a phone app that records a constant stream of audio through the night, then provides a minute-to-minute graph of my breathing health every morning. A night vision security camera just above the bed monitors every movement.
Inflammation in the throat and polyps both contribute to snoring and sleep apnea. Nasal obstruction triggers this nighttime choking as well, but nobody knows how quickly the damage comes on, or how severe it might become. Before now, nobody had tested it.