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61 " The amygdala grows particularly lively when we are asleep, and thus may account for why our dreams are so often disturbing. Your nightmares may simply be the amygdalae unburdening themselves.*2 "
― Bill Bryson , The Body: A Guide for Occupants
62 " And it is surely astounding to reflect that not once in the three billion years since life began has your personal line of descent been broken. "
63 " Viruses are a little weird, not quite living but by no means dead. Outside living cells, they are just inert things. They don’t eat or breathe or do much of anything. They have no means of locomotion. We must go out and collect them—off door handles or handshakes or drawn in with the air we breathe. They do not propel themselves; they hitchhike. Most of the time, they are as lifeless as a mote of dust, but put them into a living cell, and they will burst into animate existence and reproduce as furiously as any living thing. Like bacteria, they are incredibly successful. The herpes virus has endured for hundreds of millions of years and infects all kinds of animals—even oysters. They are also terribly small—much smaller than bacteria and too small to be seen under conventional microscopes. If you blew one up to the size of a tennis ball, a human would be five hundred miles high. A bacterium on the same scale would be about the size of a beach ball. "
64 " A child half your height who falls and strikes her head will experience only 1/32 of the force of impact that a grown person would feel, which is part of the reason that children so often seem to be mercifully indestructible.15 "
65 " The average adult touches his face sixteen times an hour, "
66 " The most remarkable part of all is your DNA. You have a metre of it packed into every cell, and so many cells that if you formed all the DNA in your body into a single fine strand it would stretch ten billion miles, to beyond Pluto.8 Think of it: there is enough of you to leave the solar system. You are in the most literal sense cosmic. "
67 " For five of fifteen smells tested, humans actually outperformed dogs. "
68 " As well as strengthening bones, exercise boosts your immune system, nurtures hormones, lessens the risk of getting diabetes and a number of cancers (including breast and colorectal), improves mood, and even staves off senility. "
69 " These days the legacy newborn babies bring into the world with them isn’t a lack of nutrition, but the opposite. So they are not only being born into households where people eat more and exercise less, but have an innate and enhanced vulnerability to succumb to the diseases that poor lifestyles bring. It has been suggested that children growing up today will be the first in modern history to live shorter, less healthy lives than those of their parents. We aren’t just eating ourselves into early graves, it seems, but breeding children to jump in alongside us. "
70 " Mammograms are in fact fuzzy things. Reading them accurately is a challenging task—much more challenging than even many medical professionals realize. As Timothy J. Jorgensen has noted, when 160 gynecologists were asked to assess the likelihood of a fifty-year-old woman having breast cancer if her mammogram was positive, 60 percent of them thought the chances were 8 or 9 out of 10. “The truth is that the odds the woman actually has cancer are only 1 in 10,” writes Jorgensen. Remarkably, radiologists do little better. "
71 " You discard about a hundred billion red blood cells every day. They are a big component of what makes your stools brown. "
72 " Some of your microbes are permanent residents. Others camp out on you for a week or a month and then, like a wandering tribe, quietly vanish. "
73 " Our bones lose mass at a rate of about 1 percent a year from late middle age onward, which is of course why elderly people and broken bones are so unhappily synonymous. Broken hips are especially challenging for the elderly. About 40 percent of people over seventy-five who break their hips are no longer able to care for themselves. For many, it is a kind of last straw. Ten percent die within thirty days, and nearly 30 percent die within twelve months. As the British surgeon and anatomist Sir Astley Cooper liked to quip, “We enter the world through the pelvis and leave it through the hip. "
74 " 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. "
75 " Altogether about 80 percent of the processed foods we eat contain added sugars. Heinz ketchup is almost one-quarter sugar. It has more sugar per unit of volume than Coca-Cola. "
76 " Where body meets air, we are all cadavers. These outer skin cells are replaced every month. We shed skin copiously, almost carelessly: some twenty-five thousand flakes a minute, over a million pieces every hour. Run a finger along a dusty shelf, and you are in large part clearing a path through fragments of your former self. Silently and remorselessly we turn to dust. "
77 " The brain takes a long time to form completely. A teenager’s brain is only about 80 percent finished "
78 " It is an arresting thought that all that makes you lovely is deceased. Where body meets air, we are all cadavers. These outer skin cells are replaced every month. We shed skin copiously, almost carelessly: some twenty-five thousand flakes a minute, over a million pieces every hour. Run a finger along a dusty shelf, and you are in large part clearing a path through fragments of your former self. Silently and remorselessly we turn to dust. "
79 " As Siddhartha Mukherjee observed in The Gene: An Intimate History, humans don’t actually reproduce at all.8 Geckos reproduce; we recombine. "
80 " If you want to imagine what a disease might do if it became bad in every possible way, you could do no better than consider the case of smallpox. Smallpox is almost certainly the most devastating disease in the history of humankind. "