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Overview
Aging—not cancer, not heart disease—is the underlying cause of most human death and suffering. The same cascade of biological changes that renders us wrinkled and gray also opens the door to dementia and disease. We work furiously to conquer each individual disease, but we never think to ask: Is aging itself necessary? Nature tells us it is not: there are tortoises and salamanders who are spry into old age and whose risk of dying is the same no matter how old they are, a phenomenon known as “biological immortality.” In Ageless, Andrew Steelecharts the astounding progress science has made in recent years to secure the same for humans: to help us become old without getting frail, to live longer without ill health or disease.
Product Details
| ISBN-13: | 9780385544924 |
|---|---|
| Publisher: | Knopf Doubleday Publishing Group |
| Publication date: | 03/23/2021 |
| Pages: | 352 |
| Sales rank: | 710,574 |
| Product dimensions: | 6.40(w) x 9.00(h) x 1.40(d) |
About the Author
Read an Excerpt
1
The Age of Aging
Cast your mind back 25,000 years. It’s late on a warm spring afternoon in what we now call southern France, and you’re gathering firewood a short way from your camp. The men are out hunting, carrying spears and seeking out game like deer and bison. You and your fellow nomads look pretty much like modern humans, but life is very different—not least because of the ever-present risk that it will end suddenly.
At 28 years old you’re doing quite well for a prehistoric woman. There are risks everywhere. A tiny scratch could get infected and kill you; you could meet a sudden end in an accident or animal attack; or other prehistoric humans, hungry and desperate, could murder you in a fight. Most tragic of all, though, out of the five children you’ve given birth to, two have died—one shortly after birth from what we’d now understand to be a serious fever, and another aged three who you buried just a month ago. Prehistory is a dangerous place to live, and death seems to strike at random, often without obvious cause. There’s no understanding of germs or birth defects—perhaps you blame capricious, vengeful gods or spirits in an attempt to make sense of it all.
It’s hard for us to work out exactly how long prehistoric humans lived, not least because prehistory is defined as the period prior to written records. There were no birth certificates or insurance companies compiling detailed mortality tables. However, surveys of bones at a handful of archaeological sites, plus extrapolation from modern hunter–gatherer societies, give us some idea—and it’s at once better and worse than you might expect.
First, the bad news: life expectancy was poor, probably somewhere between 30 and 35 years. Statistically speaking, a lot of you reading this would already be dead. However, life expectancy is a number which can obscure as much as it reveals. This is because it’s an average and comes with all the attendant statistical pitfalls. The main reason that it was so strikingly low in prehistory was the appalling rate of infant and child mortality. Infections in the first few years of life struck down many, many babies and children. You probably had only a 60 percent chance of making it to 15 years old—barely better than tossing a coin. This huge number of deaths at young ages drags down the average age at death significantly.
However, if your coin came up heads and you made it to your late teens, you could expect to live another 35 or 40 years, taking you comfortably into your fifties. This “remaining life expectancy” is itself an average, so it’s quite likely that a few ancient humans did make it into their sixties or seventies—what we, in modern times, would start to call “old age.” A headline 35-year life expectancy both masks the terrible toll of childhood deaths and underplays how long the oldest early humans lived. Such is the challenge of summarizing a complex phenomenon like human lifespan with a single number.
This was the story for tens of thousands of years: eye-watering levels of child mortality held overall life expectancy down; most who made it to adulthood lived decent but not exceptionally long lives. For millennia, death was an omnipresent feature of human life, often rapid and without warning. Those who escaped the capricious clutches of infectious disease, injury or bad luck were greeted by an inexplicable state of decline which we’d now recognize as aging: a gradual loss of faculties in a world where fitness, keen senses and mental acuity could be the difference between eating and being eaten.
It can be tempting to think of prehistoric humans as primitive, but their brains were actually very similar to our own; it seems likely that this constant, senseless loss would take its toll. While we can only speculate, there are sites where human or pre-human remains are found together, suggesting some kind of deliberate disposal of the dead. There’s an ongoing debate about when exactly funeral rituals arose—many, of course, would leave no trace which could survive the intervening millennia. But, if these sites are what they appear, funeral behavior could date back tens or even hundreds of thousands of years, to a time before our species, Homo sapiens, when our hominin ancestors walked, and aged, upon the Earth. As we transition into recorded history, our preoccupation with death is hard to deny: increasingly extravagant structures culminating in the pyramids of ancient Egypt formed the engineering pinnacle of increasingly rich mythologies surrounding life and its end.
Given this, it’s perhaps not surprising that some of the earliest philosophers grappled with aging and death. In ancient Greece, Socrates and Epicurus were unworried by dying, believing that it would be like eternal dreamless sleep. Plato was similarly sanguine, but for different reasons: he believed that our immortal souls would go on existing even after our bodies had ceased to. Aristotle was more concerned by death, and arguably the first philosopher to make a serious attempt to explain aging scientifically in 350 bce. His central thesis was that it was a process by which humans and animals dry out; as you will note from its absence in the rest of this book, sadly his theory hasn’t stood the test of time.
Even as schools of philosophy, religions and empires rose and fell, surprisingly little changed about lifespans for thousands of years. A family moving to London in 1800, looking for work as England industrialized, would have a surprisingly similar tale to tell as their nomadic ancestors, statistically at least. The exact causes of death were quite different—fewer hunting accidents, more factory accidents, and a different spectrum of infectious diseases at home in densely populated urban centers rather than small, nomadic groups—but the result was much the same: high birth rates, high death rates. By this time in history we do finally have some actual data to go on—the two countries whose records stretch back the furthest are the UK and Sweden, and both show an overall life expectancy somewhere around forty years in the early nineteenth century.
As the 1800s got into full swing, things finally began to change. Slowly, between 1830 and 1850, graphs of life expectancy start to pull up. If we take the leading country in the world at any given time, which we can regard as the state of the art in population health for any given moment in history, a very striking picture emerges. The maximum global life expectancy has increased by three months every year since 1840, with clockwork regularity. Even better, the trend shows no sign of abating. Predicting the future is always hard, but you could do worse than to extrapolate this trend of nearly two centuries onwards into it. That means (if you’re middle-aged or younger), for every year you stay alive your expected date of death recedes a few months into the future. Alternatively, for every day you survive, you gain another six hours—meaning that a good night’s sleep isn’t really time wasted, as you’re getting most of it back thanks to rising life expectancy.
The cumulative effect of this incredible progress is that lives are now twice as long on average as they were in the early 1800s—life expectancy has gone from 40 years back then, to over 80 in the rich world today. It’s easy to be glib about this meteoric rise because it’s so familiar, so take a moment and transpose those dry numbers onto your own life. At 40, you’d be statistically dead in 1800; now, you’ve got as much life again still in front of you. A 20-year-old today has better odds of having a living grandmother than a 20-year-old in the 1800s did of having a living mother. In a bare couple of centuries—perhaps 0.1 percent of the total timeline of our species—we’ve already redefined (indeed, doubled) what it means to be human. Families are now multigenerational, we can plan for the long term under the assumption we’ll live to see it, retirement is more than a few years of ill health for a handful that make it that far. For the first time in human history, the majority of babies born today will have the chance to grow old.
The straightness of the line showing life expectancy increasing is almost suspicious, because those improvements are underpinned by a tangle of cultural shifts, public health measures and scientific and medical breakthroughs happening more or less at random. And yet, every year: three more months. Successive phases of this revolution have been driven by very different phenomena. It started with the taming of humanity’s greatest ancient foe: infectious disease.
Pandemics are a humbling reminder of the power of nature compared to our own. The coronavirus crisis has laid bare what many of us had largely forgotten: the terrible toll infectious disease can take without treatments or vaccines. Nonetheless, your risk of death from COVID-19 is still substantially less than the risk from infections in the past—taken over the whole of human history, bacteria, viruses and other microorganisms have probably struck down more of us than anything else. Even in the worst case, the consequences of coronavirus are unlikely to exceed those of the 1918 flu pandemic: during that outbreak, 50 to 100 million died over a couple of years at the hands of flu viruses—up to 5 percent of the global population at the time—dwarfing the 20 million killed in the preceding four years of mechanised annihilation in the First World War. Humanity would do well to remember that our real enemy is not one another.
However, through the 1800s, unhygienic towns and cities were refitted, open sewers replaced, public health initiatives began to take root and infectious disease began to decrease. Science and medicine entered the fray, first with vaccines, and then germ theory, demonstrating that it was tiny, invisible organisms—not bad air or bad luck—that drove infection. Vaccination has since wiped smallpox from the face of the planet (albeit shockingly recently, in 1977), is well on the way to doing the same for polio, and has made former childhood specters like diphtheria and whooping cough so infrequent as to sound antique. Improved fertilizers and mechanization of agriculture ushered in better nutrition population-wide, leading to healthier children and adults better able to fend off many causes of death, infections included. At the same time, the twin engines of education and economic growth were lifting millions out of poverty, compounding the improvements in food and cleanliness. Better health and increasing longevity also bolstered the economy, in a virtuous circle of burgeoning health.
In 1850, life expectancy at birth was around 45 years in chart-topping Norway. By 1950, Norwegians (who reclaimed the crown after nearly a century of dominance by New Zealand) could expect to live beyond 70. Progress was largely driven by improvements in early and mid-life. Infectious diseases disproportionately struck children, but were also prevalent in adulthood—and their reduction dramatically increased life expectancy overall.
It’s in the last seventy years or so that improved life expectancy at older ages has finally started to move the needle on life expectancy overall, mainly due to huge strides in medical science and healthcare provision, and healthier lifestyles. Taking a survey of other essentials of modern medicine—automatic defibrillators, stents, dedicated coronary care units in hospitals, heart bypass surgery—you’ll find that none of these was available in 1950. Even cardiopulmonary resuscitation, or CPR, which uses chest compressions to restart a stopped heart and is a staple of TV drama to the point of cliché, hadn’t been invented yet. Also missing were preventative drugs like statins which lower cholesterol and make heart disease less likely to happen in the first place. And all of this is just in the world of cardiology. Drugs, devices and surgical techniques have improved outcomes for people with many different diseases at all ages, but their effect has been particularly important for the survival chances of older people. This is because, since we have massively reduced infectious disease, the deadliest health problems today are things like heart disease and cancer, which primarily hit later in life.
Of the improvements in lifestyle, the single biggest has been the decline in smoking. It’s shocking, but the shadow of a single industry—indeed, by and large a single product, the cigarette—is cast over life expectancy statistics across half a century. In the U.S. in the 1960s, cigarette consumption was high enough for every adult to smoke more than half a pack a day. This generation of long-term smokers created a population-wide crescendo of smoking-related diseases which, because it takes time for smoking to cause disease and death, peaked a few decades later in the 1980s and 1990s—at which time around a sixth of all deaths (and a staggering 25 percent of male deaths) in the developed world were attributable to tobacco. In total, there are estimated to have been 100 million deaths from smoking in the twentieth century. Smoking rates have more than halved since their peak, and are still dropping—and that drop is now showing up in life expectancy statistics.
The cumulative result of all of this can be seen in global tables of life expectancy: the country with the highest life expectancy in 2019 was Japan, whose citizens live to 84.5 years old on average. And there are plenty of others snapping at its heels—the top 30 countries in the global rankings all have life expectancies above 80 years.
As well as extending lifespan, we’ve also been extending healthspan. A study looking at changes in the UK between 1991 and 2011 found that life expectancy at age 65 had risen by about four years, and so had the number of years spent without cognitive impairment, and, if you ask people to rate their own health in a survey, the number of years spent healthy went up by a similar amount again. Improvements in health are most pronounced in the very old: the fraction of over-85s in the U.S. classified as disabled dropped by a third between 1982 and 2005, while the number who are institutionalized almost halved over the same period, from 27 to 16 percent. Depending on how you measure health or disability, the fraction of our lives spent in ill health is either shrinking or roughly constant, both of which are good news.
Table of Contents
Introduction 1
Part I An Age-Old Problem
1 The Age of Aging 17
2 On the Origin of Aging 32
3 The Birth of Biogerontology 52
4 Why We Age 70
Part II Treating Aging
5 Out with the Old 111
6 In with the New 138
7 Running Repairs 169
8 Reprogramming Aging 207
Part III Living Longer
9 The Quest for a Cure 241
10 How to Live Long Enough to Live Even Longer 246
11 From Science to Medicine 270
Acknowledgments 287
Notes and Bibliography 291
Index 331
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