The Body - interesting facts

I highly recommend the book "The Body: A Guide for Occupants." by Bill Bryson. 

It is intriguing and interesting reading in every paragraph. It's well researched: he seems to have not only consulted the best experts, but known exactly what questions to ask them to draw out the most intriguing information. Here are a few excerpts. 

If you formed all the DNA in your body into a single strand, it would stretch ten billion miles, to beyond Pluto. p 5

[DNA] is exquisitely thin. You would need twenty billion strands laid side by side to make the width of the finest human hair. p6

Melanin, one of the oldest molecules in biology...gives...squid the purply blackness of their ink. p15

It therefore became a great advantage to have lighter skin, to synthesize extra vitamin D. p16

The number of bacteria on you actually rises after a bath or shower because they are flushed out from nooks and crannies. p24

Belly buttons swabbed...found 2368 species of bacteria, 1458 of which were new to science. p25

Humans produce twenty digestive enzymes, which is a pretty respectable number in the animal world, but bacteria [that we host in our gut] produce ten thousand. p28

Bacteria can swap genes among themselves, as if they were Pokemon cards, and they can pick up DNA from dead neighbors... 🧬the DNA of bacteria is less scrupulous in its proofreading, too, so they mutate more often, giving them even greater genetic nimbleness. The average bacterium...lives for no more than twenty minutes...which means that in three days they can rack up as many new generations as we have managed in the whole of human history. p29

You have about twenty thousand genes of your own within you, but perhaps as many as twenty million bacterial genes, so from that perspective you are roughly 99% bacterial. p30-1

Surprisingly, the least effective way to spread germs is kissing. It proved almost wholly  ineffective among volunteers who had been successfully infected with cold virus. Sneezes and coughs weren't much better. The only reliable way to transfer cold germs is physically by touch...metal poles are a fairly hostile environment for microbes. Where microbes thrive is on fabrics on seats and on plastic handgrips. The most efficient method of transfer for germs, it seems, is a combination of folding money and nasal mucus...virus can survive on paper money for 2 1/2 weeks if it is accompanied by a microdot of snot.  p35

To your brain, the world is just a stream of electrical pulses, like taps of Morse code. And out of this bare and neutral information it creates for you - quite literally creates - a vibrant, three-dimensional, sensually engaging universe. Your brain is you. Everything else is just plumbing and scaffolding. p49

For each visual input, it takes a tiny but perceptible amount of time - about two hundred milliseconds, one-fifth of a second - for the information to travel along the optic nerves and into the brain to be processed and interpreted. One-fifth of a second is not a trivial span of time when a rapid response is required - to step back from an oncoming car, say, or to avoid a blow to the head. 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. p55

"The teenage brain is not just an adult brain with fewer miles on it (Frances E. Jensen)... It is, rather, a different kind of brain altogether...the body produces more dopamine, the neurotransmitter that conveys pleasure, than it ever will again. That is why the sensations you feel as a teenager are more intense than at any other time in life. p.63

[Frontal lobotomies:] Moniz provided an almost perfect demonstration of how not to do science. He undertook operations without having any idea what damage they might do or what the outcomes would be. He conducted no preliminary experiments on animals. He didn't select his patients with particular care and didn't monitor outcomes closely afterward. He didn't actually perform any of the surgeries himself, but supervised his juniors - though freely took credit for any successes. p. 65

Most other mammals never suffer strokes, and for those that do, it is a rare event. But for humans, it is the second most common cause of death globally...we have an excellent blood supply to the brain to minimize stroke and yet we get strokes. p. 68

Well into the twentieth century, it was commonly believed by medical authorities that seizures were infectious - that just watching someone have a seizure could provoke a seizure in others... As recently as 1956, it was illegal in seventeen US states for epileptics to marry; in eighteen states, epileptics could be involuntarily sterilized. p. 68

Daniel McNeill - Men were shown two photos of women that were identical in every respect except that the pupils had been subtly enlarged in one. Although the change was too slight to be consciously perceived, the test subjects invariably found the women with larger pupils more attractive, though they were at a loss to explain why.

(Paul Ekman) we all indulge in "microexpressions" - flashes of emotion, no more than a quarter of a second in duration, that betray our true inner feelings regardless of what our more general, controlled expression is conveying. p. 78

Because we were once nocturnal, our ancestors gave up some color acuity - that is, sacrificed cones for rods - to gain better night vision. Much later, primates re-evolved the ability to see reds and oranges, the better to identify ripe fruit, but we still have just three color receptors compared with four for birds, fish and reptiles. p. 83

A pressure wave that moves the eardrum by less than the width of an atom will activate the ossicles and reach the brain as sound. p.85

Swallowing is a trickier business than you might think. Altogether, fifty muscles can be called into play just to get a piece of food from your lips to your stomach, and they must snap to attention in exactly the right order. p. 95

Taste buds...are among the most regenerative of all cells in the body and are replaced every ten days. p. 101

MSG is the food additive that had been subjected to the most through scrutiny of all time, and no scientist has ever found any reason to condemn it, yet it's reputation in the West as a source of headaches and low-grade malaise now appears to be undimmed and permanent. p.106

The heart...beats...as many as 3.5 billion times in a lifetime. p.112

[100 years = 100*365.25*24*60*60  = 3.15 billion seconds]

Sandoz [employee] Frey, while on holiday in Norway, collected soil samples to take back to the Sandoz labs [which] contained a fungus...which had no useful antibiotic properties, but proved excellent at suppressing immune responses...cyclosporine. p.122

In the United States, [blood] plasma sales make up 1.6% of all goods exported, more than America earns from the sale of airplanes. p. 126

[Banting and Best's experiments] were "wrongly conceived, wrongly conducted, and wrongly interpreted." Yet within weeks they were producing pure insulin. p. 139

Nothing chemical in your body is...programmed to tell you to stop eating...We are habituated into devouring foods greedily whenever we are able on the assumption that abundance is an occasional condition. p. 147

The most powerful impression you get in a dissecting room is that the human body is not a wondrous piece of precision engineering. It's meat.... The liver, pancreas, kidneys, spleen...there's a lot of other stuff in there, too... All of it just kind of tipped in, as if this poor, anonymous, former person had had to pack himself in a hurry. p. 158-9

Cartilage...is many times smoother than glass: it has a friction coefficient five times less than ice. p. 160

Collagen is the most abundant protein in the body ; 40% of all your proteins are collagens. p.166

All your bones together weigh no more than about 20 pounds, yet most can withstand up to a ton of compression. Bone is the only tissue in the body that won't scar...after it heals you cannot tell where the break was. p. 166

The femur angles inwards as it descends from pelvis to knee. This has the effect of moving our lower legs closer together, giving us a much smoother, more graceful gait...a chimpanzee uses four times as much energy to move around at ground level as does a human. p. 175

Our transformation [to walking upright] was a two-stage process. First, we became walkers and climbers, but not runners. Then we became walkers and runners, but no longer climbers. p.177

Modern hunter-gatherer [tribesmen] average about 19 miles of walking and trotting to secure a day's food. p. 180

The current generation of young people is forecast to be the first in recorded history not to love as long as their parents because of weight-related health issues. p.181

Every day you produce and consume your own body weight in ATP molecules... Because ATP is consumed more or less instantaneously you have only 60 grams of it within you at any given moment. p. 191

Humans can manage to live on only about 12% of Earth's land area and just about 4% of the total surface area if you include the seas. It's a sobering thought that 96% of our planet is off limits to us. p.193

Horrifying as the German experiments were, they were outdone, in scale of not cruelty, by the Japanese. Under a doctor named Shiro Ishii, the Japanese built an enormous complex...with the avowed purpose of determining human physiological limitations through any means necessary... Chinese prisoners were tied to stakes at staggered distances from a shrapnel bomb...noting the extent of the prisoner's injuries and how long it took them to die... Others were shot with flamethrowers, starved, frozen or poisoned. p.197

Take Crohn's disease...before 1932 when Burrill Crohn [first] described it...affected one person in 50,000. Today the proportion is one in 250 and still rising. p. 208

The richer the country, the more allergies its citizens get...there is evidence that nitrogen oxides from diesel fuels correlate with higher incidences of allergies. p.209

Every time you breathe, you exhale some 2.5E22 molecules of oxygen - so many that with a day's breathing [20,000 breaths per day] you will in all likelihood inhale at least one molecule from the breaths of every person who has ever lived. p. 212

The second half of the twentieth century saw a rapid increase in asthma rates in most Western nations, and no one knows why. p. 217

Cooking [our food] confers all kinds of benefits. It kills toxins, improves taste, makes tough substances chewable, greatly broadens the range of what we can eat, and above all vastly boosts the amount of calories humans can derive from what they eat. p.229

Vitamins are a surprisingly recent concept...he called them "vitamines," a contraction of "vital" and "amines"... Even today, vitamins are an ill-defined entity. The term describes thirteen chemical oddments that we need to function smoothly but are unable to manufacture for ourselves... Though we think of them as closely related, they mostly have little in common apart from being useful to us. They are sometimes described as "hormones made outside the body." p. 231-2

Curiously, too much or too little iron both provide the same symptom, lethargy... Too much...causing our organs literally to rust. p. 233

What can be said with some confidence is that many people have a faith in health supplements that goes way beyond the fully rational. p. 233

About a million different proteins have been identified so far...they are all made from just twenty amino acids, even though hundreds of amino acids exist in nature that could do the job just as well. Why evolution has wedded us to such a small number of amino acids is one of the great mysteries of biology. p. 234

In 2015 - almost sixty years after Kummerow first reported the dangers - did the FDA finally decree trans fats unsafe to eat. Despite their known dangers, it remained legal to add them to foods in America until 2018. p. 238

Over a lifetime, we eat about sixty tons of food... In 1915, the average American spent about half his weekly income on food. Today is just six percent. p. 239

Modern fruits, for instance, are about 50 percent poorer in iron than they were in the early 1950's, and about 12 percent down in calcium and 15 percent in vitamin A. p. 243

"There's a really easy way to do food shopping in supermarkets. Just stick to the outside aisles. The aisles in between are almost entirely filled with processed foods. If you stick to the outside, you will automatically have a healthier diet." p. 248

84% of chicken breasts, nearly 70% of ground beef, and getting on for half of pork chops contain E. coli. p. 249-50

The largest source of foodborne illness is not meat or eggs or mayonnaise, as commonly supposed, but green leafy vegetables. They account for one in five of all food-borne illnesses. p. 252

Teenagers'...circadian cycles can be up to two hours adrift from those of their elders...86% of US high schools start their day before 08:30... Later start times have been shown to produce better attendance, better test results, fewer car accidents, and (even) less depression and self harm. p. 270

As late as 1932, one mother in every 238 died in (or from) childbirth. [now 1:6000] Partly for these reasons, women continued to shun hospitals, well into the modern era.  Into the 1930s, fewer than half of American women gave birth in hospitals. p. 296

Nursing mothers produce over two hundred kind of complex sugars, oligosaccharides, in their milk that their babies cannot digest because humans lack the necessary enzymes. The oligosaccharides are produced purely for the benefit of the baby's gut microbes - as bribes, in effect. p. 301

The US has 4% of the world's population but consumes 80% of it's opioids. p. 315

What it comes down to is cancer is, appallingly, your own body doing its best to kill you. It is suicides without permission. p.337

[Cancer cells] have evolved to avoid detection... They can hide from drugs, develop resistance, recruit other cells to help them, go into hibernation and wait for better conditions. p. 337-8

Cancer is the price we pay for evolution. If our cells couldn't mutate, we would never get cancer, but we also wouldn't evolve. p. 338

An 80 year old is a thousand times more likely than a teenager to develop cancer. p.339

In 1911, Peyton Rous...found that a virus caused cancer in chickens...the discovery was universally dismissed...1966...he was formally vindicated with the award of a Nobel prize... It has been estimated, pathogens may account for a quarter of all cancers...p. 340-1

Lawrence Henderson remarked, "At some point between 1900 and 1912, a random patient with a random disease, consulting a doctor chosen at random, had for the first time in history a better than fifty-fifty chance of profiting from the  encounter. p. 355

Two things can be said with confidence about life expectancy in the world today. One is that it is really helpful to be rich... The second thing...is that it is not a good idea to be American... randomly selected American aged 45-54 is twice as likely to die, from any cause, as someone in the same age group in Sweden... Children in USA are 70% more likely to die in childhood than children in the rest of the wealthy world. Among rich countries, America is at or near the bottom for virtually every measure of medical well-being... Counterintuitive when you consider that America spends more on health care than any other nation...$10K per citizen...p. 358-9 [<2019]

Breast cancer screening doesn't save a lot of lives. For every thousand women screened, four will die of breast cancer anyway (either because the cancer was missed or because it was too aggressive to be treated successfully.) For every thousand women who are not screened, five will die of breast cancer. So screening saves one life in every thousand. p.362 [this ignores years of life gained by screening]

The Hayflick limit...the idea that cells possess some form of memory and can count down toward their own extermination was so wildly radical that it was almost universally rejected. p. 371

Antioxidant supplementation did not lower the incidence of many age-associated diseases but, in some cases, increased the risk of death. p. 372

We are they only primates that undergo menopause, and one of only a very few animals...It is a myth that menopause is triggered by women exhausting their supply of eggs. They still have eggs. Not many, to be sure, but more than enough to remain fertile. p. 373