Nestor got himself into a Stanford lab and had a rhinologist plug both his nostrils shut with silicone for ten days, which left him breathing through his mouth and nothing else. His blood pressure spiked, he started snoring 4,000 percent more, and sleep apnea set in. Then they pulled the plugs, he spent ten days breathing through his nose, and it all reversed. That experiment is the spine of the book.
He handles ancient skulls at a museum in Philadelphia and finds wide jaws and straight teeth, then explains how softer food and less chewing narrowed the human face and closed down the airway. He tracks down the outsiders who worked pieces of this out on their own — a Russian doctor, a choir conductor who taught emphysema patients to exhale, Wim Hof in the ice. The takeaways are absurdly simple —breathe through your nose, breathe slower, exhale longer, and quit thinking about carbon dioxide as waste — but you still should investigate the book for yourself. After reading the drawbacks of mouth-breathing during sleep, I started taping my mouth closed and my sleep quality improved dramatically. Maybe not 4,000 percent, but close. (Insert jokes about taping my mouth shut during waking hours here.)