Far From a Yawn

If there was a book I would give a young student interested in medicine, it would be Bill Bryson’s The Body: A Guide for Occupants. Written in a lighthearted conversational manner, it is chock full of interesting factoids illustrated by engaging vignettes. Bryson is a master story-teller.

Reading The Body amidst the Covid-19 pandemic has further heightened my senses towards all things human-health-related. When reading the chapter on the immune system, I found myself looking up more details on the internet. The chapter on bipedalism and exercise reminded me to get up, stand, and walk, more regularly; my sedentary seated in front of a computer lifestyle is a problem. I thought about what I eat as I read the chapter on digestion. And of course, I found anything on chemistry interesting; the chapter on endocrinology is appropriately titled “The Chemistry Department”.

There are many historical anecdotes sprinkled throughout the text. Stories of discovery are interesting in their own right, but what really struck me in these accounts was how difficult it could be for others to accept these discoveries. There’s the oft-told story of Semmelweis, who “discovered” the importance of doctors washing their hands properly before surgery, but was disbelieved by many of his contemporaries who couldn’t imagine that they would be the cause of patient infection. Sometimes science was moved forward even when the initial ideas were wrongheaded; for example Atwater’s caloric measurements leading to his proposal that we should all eat lots of meat since it was a superior fuel source!

Bryson debunks some seemingly “well-known facts”. You’ve probably heard that bacteria cells in our body outnumber our own cells ten-to-one. Apparently, this was from a 1972 paper that was guesswork, and that in 2016, scientists making careful measurements found the ratio to vary between two-to-one and one-to-one. Not only had I believed this for years, I also believed that drinking coffee and other diuretics make me lose water overall. Turns out that while “not the most wholesome of options for liquid refreshment, they do make a net contribution to your personal water balance.”

While Bryson illuminates the reader with history, discovery, and many factoids, he also points out, in most chapters, how much we don’t know. We know a lot about the human body, but it’s amazing how much we don’t know. For example, sleep is still mysterious although we know a lot about it. Rising cases in asthma or Crohn’s disease, while attributed (sometimes speculatively) to a variety of factors, remain a bit of a puzzle. Or consider the uvula. We think it helps with food direction down the throat, maybe aids in producing saliva, or helps with creating certain speech sounds including snoring sounds; but when folks have it removed (due to snoring), it’s unclear what else is impaired.

I’ll end by quoting Bryson as he describes one of those things we don’t know, to illustrate his engaging and whimsical writing.

Finally, we should say a word about that mysterious but universal harbinger of weariness, the yawn. No one understands why we yawn. Babies yawn in the womb. (They hiccup, too.) People in comas yawn. It is a ubiquitous part of life and yet what exactly it does for us is unknown. One suggestion is that it somehow connected with shedding excess carbon dioxide, though no one has ever explained in what way. Another is that it brings a rush of cooler air into the head, thus slightly banishing drowsiness, though I have yet to meet anyone who felt refreshed and energized after yawning. More to the point, no scientific study has ever shown a relationship between yawning and energy levels. Yawning doesn’t even correlate reliably with how tired you are. Indeed, when we yawn the most is often in the first couple of minutes after rising from a good night’s sleep, when we are at our most rested.

I highly recommend The Body. It’s far from a yawn!