The Body

Title: The Body: A Guide for Occupants

Author: Bill Bryson

Overview: An amazing look at the body, what we know about how it works and just how much we really don’t understand. As with his previous book, “A Short History of Nearly Everything”, he does a good job telling stories about the people who made the discoveries that changed our understanding of the body. This helps prevent it from reading like a textbook.


  • My DNA and your DNA will differ in three to four million places, which is a small proportion of the total but enough to make a lot of difference between us. You also have within you about a hundred personal mutations—stretches of genetic instructions that don’t quite match any of the genes given to you by either of your parents but are yours alone.
  • Five out of every six smokers won’t get lung cancer. Most of the people who are prime candidates for heart attacks don’t get heart attacks. Every day, it has been estimated, between one and five of your cells turn cancerous, and your immune system captures and kills them.
  • If you put all Earth’s microbes in one heap and all the other animal life in another, the microbe heap would be twenty-five times greater than the animal one.
  • Antibiotics are about as nuanced as a hand grenade. They wipe out good microbes as well as bad. Increasing evidence shows that some of the good ones may never recover, to our permanent cost. Most people in the Western world, by the time they reach adulthood, have received between five and twenty courses of antibiotics. The effects, it is feared, may be cumulative, with each generation passing on fewer microorganisms than the one before.
  • To help us deal better with this fractional lag, the brain does a truly extraordinary thing: it continuously forecasts what the world will be like a fifth of a second from now, and that is what it gives us as the present. That means that we never see the world as it is at this very instant, but rather as it will be a fraction of a moment in the future. We spend our whole lives, in other words, living in a world that doesn’t quite exist yet.
  • Incidentally, the idea that we use only 10 percent of our brains is a myth. No one knows where the idea came from, but it has never been true or close to true. You may not use it all terribly sensibly, but you employ all your brain in one way or another.
  • According to Daniel Lieberman, professor of human evolutionary biology at Harvard, our external nose and intricate sinuses evolved to help with breathing efficiency and with keeping us from becoming overheated on long runs.
  • To help protect us from the damage of really loud noises, we have something called an acoustic reflex, in which a muscle jerks the stapes away from the cochlea, essentially breaking the circuit, whenever a brutally intense sound is perceived, and it maintains that posture for some seconds afterward, which is why we are often deafened after an explosion. Unfortunately, the process is not perfect. Like any reflex, it is quick but not instantaneous, and it takes about a third of a second for the muscle to contract, by which point a lot of damage can be done.
  • Still other chemicals have very different structures but produce the same smell, and no one knows why that happens either. The smell of burned almonds can be produced by seventy-five different chemical combinations that have nothing in common beyond how the human nose perceives them.
  • It has been calculated (and goodness knows how, it must be said) that during the course of a lifetime the heart does an amount of work sufficient to lift a one-ton object 150 miles into the air.
  • A woman is more likely to experience abdominal pain and nausea than a man, which makes it more likely that the problem will be misdiagnosed. Partly for this reason, women who have heart attacks before their mid-fifties are twice as likely to die as a man.
  • Altogether the liver takes part in some five hundred metabolic processes. It is essentially the body’s laboratory. Right now, about a quarter of all your blood is in your liver.
  • osteocalcin, which is produced in bones, not only is a hormone but seems to be involved in a large number of important regulatory activities across the body, from helping to manage glucose levels to boosting male fertility to influencing our moods and keeping our memory in working order. Apart from anything else, it could help to explain the long-standing mystery of how regular exercise helps to stave off Alzheimer’s disease: exercise builds stronger bones and stronger bones produce more osteocalcin.
  • At the back of your head is a modest ligament, not found on other apes, that instantly betrays what it is about us that allowed us to thrive as a species. It is the nuchal ligament, and it has just one job: to hold the head steady when running. And running—serious, dogged, long-distance running—is the one thing we do superlatively well.
  • First, we became walkers and climbers, but not runners. Then, gradually, we became walkers and runners, but no longer climbers. Running is not just a faster form of locomotion than walking but mechanically quite different.
  • An analysis of 655,000 people in 2012 found that being active for just eleven minutes a day after the age of forty yielded 1.8 years of added life expectancy. Being active for an hour or more a day improved life expectancy by 4.2 years.
  • British academic Steve Jones, a test subject ran a marathon on a treadmill while the room temperature was gradually raised from minus 49 degrees Fahrenheit to 131 degrees Fahrenheit—roughly the limits of human tolerance at both extremes. Despite the subject’s exertions and the great range of temperatures, his core body temperature deviated by less than one degree over the course of the exercise.
  • Even with the advantage of clothing, shelter, and boundless ingenuity, humans can manage to live on only about 12 percent of Earth’s land area and just 4 percent of the total surface area if you include the seas. It is a sobering thought that 96 percent of our planet is off-limits to us. The thinness of the atmosphere puts a
  • Children who sit watching television not only are not exercising their lungs as they would if they were at play but even breathe differently from children who are not transfixed by a screen. Specifically, children who are reading take deeper breaths and sigh more often than children watching TV, and that slight difference in respiratory activity may be enough to increase TV watchers’ susceptibility to asthma, according to this theory.
  • Although all proteins are made from amino acids, there is no accepted definition as to how many amino acids you need in a chain to qualify as a protein. All that can be said is that a small but unspecified number of amino acids strung together is a peptide. Ten or twelve strung together is a polypeptide. When a polypeptide begins to get bigger than that, it becomes, at some ineffable point, a protein.
  • As Lieberman has noted, modern fruits have been selectively bred to be vastly more sugary than they once were. The fruits that Shakespeare ate were, for the most part, probably no sweeter than the modern carrot.
  • Modern fruits, for instance, are almost 50 percent poorer in iron than they were in the early 1950s, and about 12 percent down in calcium and 15 percent in vitamin A. Modern agricultural practices, it turns out, focus on high yields and rapid growth at the expense of quality.
  • One curious fact is that animals that are hibernating also have periods of sleep. It comes as a surprise to most of us, but hibernation and sleep are not the same thing at all, at least not from a neurological and metabolic perspective. Hibernating is more like being concussed or anesthetized: the subject is unconscious but not actually asleep. So a hibernating animal needs to get a few hours of conventional sleep each day within the larger unconsciousness.
  • How exactly melatonin relates to sleep is still not understood. Melatonin levels within us rise as evening falls and peak in the middle of the night, so it would seem logical to associate them with drowsiness, but in fact melatonin production also rises at night in nocturnal animals when they are most active, so it is not promoting sleepiness.
  • The good news is that for most women in the world childbirth has become vastly safer. In the first decade of the twenty-first century, only eight countries in the world saw their rates of childbirth deaths increase. The bad news is that the United States was one of those eight. “Despite its lavish spending, the United States has one of the highest rates of both infant and maternal death among industrialized nations,” according to The New York Times.
  • There is no pain center in the brain, no one place where pain signals congregate. A thought must travel through the hippocampus to become a memory, but a pain can surface almost anywhere. Stub your toe and the sensation will register across one set of brain regions; hit it with a hammer and it will light up others. Repeat the experiences, and the patterns may change yet again.
  • Other studies have shown that people given a colored tablet with corners will report feeling better than when given a plain white tablet. Red pills are deemed more fast acting than white pills. Green and blue pills have a more soothing effect. Patrick Wall, in his book on pain, reported how one doctor got good results from handing his patients pills held in a forceps, explaining that they were too potent to be held by bare fingers. Extraordinarily, placebos are even effective when people know they are placebos.
  • In London, life expectancy drops reliably by one year for every two stops traveled eastward from Westminster on the District Line of the Underground. In St. Louis, Missouri, make a twenty-minute drive from prosperous Clayton to the inner-city Jeff-Vander-Lou neighborhood and life expectancy drops by one year for every minute of the journey, a little over two years for every mile. Two things can be said with confidence about life expectancy in the world today. One is that it is really helpful to be rich. If you are middle-aged, exceptionally well-off, and from almost any high-income nation, the chances are excellent that you will live into your late eighties. Someone who is otherwise identical to you but poor—exercises as devotedly, sleeps as many hours, eats a similarly healthy diet, but just has less money in the bank—can expect to die between ten and fifteen years sooner. That’s a lot of difference for an equivalent lifestyle, and no one is sure how to account for it. The second thing that can be said with regard to life expectancy is that it is not a good idea to be an American. Compared with your peers in the rest of the industrialized world, even being well-off doesn’t help you here.
  • A randomly selected American aged 45 to 54 is more than twice as likely to die from any cause as someone from the same age-group in Sweden.
    • America has about 800,000 practicing physicians but needs twice that number of people to administer its payments system. The inescapable conclusion is that higher spending in America doesn’t necessarily result in better medicine, just higher costs.