Photo by Robert Riger/Getty Images 
 
 Lifespan has doubled in the United States in the past 150 years. This ridiculously wonderful change in the nature of life and death is something we tend to take for granted. When we do think about why we’re still alive, some of the big, fairly obvious reasons that come to mind are vaccines, antibiotics, clean water, or drugs for heart disease and cancer. But the world is full of underappreciated people, innovations, and ideas that also save lives. A round of applause, please, for some of the oddball reasons, in no particular order, why people are living longer and healthier lives than ever before. 
 
 Laura Helmuth Laura Helmuth is the health, science, and environment editor at the Washington Post. From 2012–2016, she was Slate’s science and health editor. Follow her on Twitter. 
 
 Photo by Thinkstock 
 
 Cotton. One of the major killers of human history was typhus, a bacterial disease spread by lice. It defeated Napoleon’s army; if Tchaikovsky’s 1812 Overture were historically accurate, it would feature less cannon fire and more munching arthropods. Wool was the clothing material of choice before cotton displaced it. Cotton is easier to clean than wool and less hospitable to body lice. 
 
 Photo by NASA via Getty Images 
 
 Satellites. In 1900, a hurricane devastated Galveston, Texas. It killed 8,000 people, making it the deadliest hurricane in U.S. history. In 2008, Hurricane Ike hit Galveston. Its winds were less powerful at landfall than those of the 1900 storm, but its storm surge was higher, and that’s usually what kills people. This time we saw it coming, thanks to a network of Earth-monitoring satellites and decades of ever-improving storm forecasting. More than 100 people died, but more than 1 million evacuated low-lying coastal areas and survived. 
 
 Fluoride. There were plenty of miserable ways to die before the mid-20th century, but dying of a tooth abscess had to be among the worst—a slow, painful infection that limits your ability to eat, causes your head to throb endlessly, and eventually colonizes the body and kills you of sepsis. Now it’s a rare way to go, thanks to modern dental care, toothbrushes, and (unless you’re in Portland) fluoridated water. 
 
 Image courtesy Library of Congress 
 
 Window screens. Houseflies are irritating today, but they used to be major vectors of deadly diarrheal disease. Clean water and treatment of sewage eliminated the most obvious means of transmitting these diseases, but pesky houseflies continued to spread deadly microbes. By the 1920s, according to James Riley in Rising Life Expectancy: A Global History, a growing aversion to insects and the introduction of window screens reduced this risk. 
 
 The discovery of unconscious bias. The reason we trust double-blind, placebo-controlled clinical trials to tell us which medical treatments actually work is that we know we can’t trust ourselves. If you take a sham drug that you think will alleviate your symptoms, it will—that’s the placebo effect. If you think the drug will cause side effects, it will—that’s the nocebo effect. If you’re a clinician and think you’re administering a real drug, you will send all kinds of signals, unintentionally, to tell the patient you think the treatment will work. If you’ve seen anecdotal evidence for a treatment, you notice confirmatory evidence rather than cases that make you revise your original hypothesis. When analyzing the data, it’s all too easy to squint at the numbers in a way that confirms your expectations. Double-blind trials overcome these biases by preventing both patient and clinician from knowing whether a tested drug is real or not. 
 
 Photo courtesy Frank Chan/Flickr via Creative Commons: http://www.flickr.com/photos/geekstinkbreath/5767003752/ 
 
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 Botts’ Dots. Those raised ceramic reflectors between road lanes were invented by Elbert Botts, a chemist who worked for the California Department of Transportation. The dots help motorists see the edge of their lane even in the dark or when it’s raining. Botts died in 1962, four years before the first Botts’ dots were installed on California highways. 
 
 Morbidity and Mortality Weekly Report. That’s the no-nonsense name of one of the most important publications most people have never heard of. The Centers for Disease Control and Prevention has been publishing it since 1952 to provide “timely, reliable, authoritative, accurate, objective, and useful public health information and recommendations.” When a new disease or danger emerges—such as AIDS or a new strain of influenza—the MMWR is often the first to identify it. 
 
 Air-conditioning. As Dan Engber pointed out in a two-part ode to A/C last summer, heat is deadly and we don’t respect it enough. A Chicago heat wave killed more than 700 people in one week in 1995. The National Weather Service issues heat alerts, and cities have started to offer air-conditioned cooling centers for people who would overheat at home. A recent study shows that air conditioning has cut the death rate on hot days by 80 percent since 1960. 
 
 The residents of Framingham, Mass. In 1948, researchers signed up more than 5,000 adults for a long-term study of heart disease. Nobody anticipated just how long-term the study would be—it’s still going strong and now includes the children and grandchildren of the original cohort. It taught us much of what we know about heart disease. Before the study, high blood pressure was thought to be a sign of good health; now it’s recognized as a risk factor for heart attacks and strokes. Thanks to the generosity and commitment of volunteers in Framingham and other studies, we know the dangers of high cholesterol, obesity, inactivity, and smoking. 
 
 Image courtesy Wikimedia Commons 
 
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 Pasteurization. This should be an obvious lifesaver, right up there with hand-washing and proper nutrition. But the rise of the raw milk movement suggests that a lot of people take safe dairy products for granted. Contaminated milk was one of the major killers of children, transmitting typhoid fever, scarlet fever, diphtheria, tuberculosis, and other diseases. One of the most successful public health campaigns of the late 19th and early 20th centuries was for pure and pasteurized milk—so successful that we don’t really remember how deadly milk can be. 
 
 Shoes. Hookworms are parasites that enter the human body through bare feet—often by biting into the soft skin between the toes (shudder). The disease was common in the Southeast, spread when people walked barefoot across ground that was contaminated with feces of people who were already infected. Education initiatives at the beginning of the 20th century encouraged people to build sanitary outhouses and wear shoes. 
 
 Cows. I mentioned in an earlier story that the Midwest—including Michigan!—once had some of the worst malaria outbreaks in the country. Anopheles mosquitoes had always flourished in the damp lowlands around streams and melting snow, and when settlers came, some of them carried Plasmodium parasites that the mosquitoes spread widely. The settlers’ farming practices made for even more stagnant water, and their sod and log houses were perfect habitat for biting pests. After farmers had exhausted the soil, they started raising cows rather than crops—and mosquitoes prefer to suck bovine blood even more than that of humans, helping break the malaria cycle. In the South and other parts of the country, larvicides, pesticides, better drainage, bug-proof housing, mechanized agriculture that replaced human labor, and fewer people living in lowlands helped eliminate malaria. 
 
 Image courtesy CDC via Wikimedia Commons 
 
 Oppressive, burdensome, over-reaching government regulations. People like to complain about the government, but when you start looking through the alphabet soup of agencies, you realize that most of them are there to save your life. The National Oceanic and Atmospheric Administration runs the National Weather Service and warns you about hurricanes. The Environmental Protection Agency enforces the Clean Air Act and has dramatically reduced the amount of deadly pollutants in the air you breathe. The Occupational Safety and Health Administration keeps you safe at work. The National Highway Traffic Safety Administration and National Transportation Safety Board investigate vehicles and accidents and make recommendations so accidents don’t happen again. The Food and Drug Administration keeps deadly microbes out of your food. The Consumer Product Safety Commission recalls toys that could kill your child. The Centers for Disease Control and Prevention tracks and tries to cure or avert basically any health hazard, and the National Institutes of Health supports some of the most important biomedical research in the world. 
 
 Goodness. Philosopher Daniel Dennett had an epiphany after emergency surgery a few years ago. It wasn’t a religious epiphany—instead of thanking God, he realized he should thank human goodness: 
 
 “To whom, then, do I owe a debt of gratitude? To the cardiologist who has kept me alive and ticking for years … the surgeons, neurologists, anesthesiologists, and the perfusionist, who kept my systems going for many hours under daunting circumstances. To the dozen or so physician assistants, and to nurses and physical therapists and x-ray technicians and a small army of phlebotomists so deft that you hardly know they are drawing your blood, and the people who brought the meals, kept my room clean. … I remember with gratitude my late friend and Tufts colleague, physicist Allan Cormack, who shared the Nobel Prize for his invention of the CT scanner. Allan—you have posthumously saved yet another life, but who's counting? The world is better for the work you did. Thank goodness. Then there is the whole system of medicine, both the science and the technology. … So I am grateful to the editorial boards and referees, past and present, of Science, Nature, Journal of the American Medical Association, Lancet, and all the other institutions of science and medicine that keep churning out improvements, detecting and correcting flaws.” 
 
 These are just a few of the countless ways people have made life safer, healthier, less painful—and longer—than we ever could have imagined a few centuries ago. Thank goodness. ||||| BACKGROUND: 
 
 On September 13, 2008, Hurricane Ike, a category 2 storm with maximum sustained winds of 110 mph, made landfall near Galveston, Texas. Ike produced a damaging, destructive, and deadly storm surge across the upper Texas and southwestern Louisiana coasts. Thirty-four Texas counties were declared disaster areas by the Federal Emergency Management Agency; 15 counties were under mandatory evacuation orders. To describe causes of death associated with this hurricane and identify prevention strategies during the response and recovery phases, the Texas Department of State Health Services (DSHS) monitored mortality data in 44 counties throughout the state. This report summarizes Ike-related deaths reported by Texas medical examiners, justices of the peace (coroners), forensic centers, public health officials, and hospitals. 
 
 METHODS: 
 
 Based on the Centers for Disease Control and Prevention (CDC) disaster-related mortality surveillance form, DSHS developed a state-specific 1-page form and collected (optimally daily) data on demographic, date and place of death, and cause and circumstance of deaths. A case was defined as any death that was directly or indirectly related to Ike among evacuees, residents, nonresidents, or rescue personnel in the declared disaster counties, counties along the Texas Gulf coast or counties known to have evacuation shelters occurring September 8, 2008, through October 13, 2008. Analyzed data were shared with the state emergency operation center and the CDC on a daily basis. 
 
 RESULTS: 
 
 The surveillance identified 74 deaths in Texas as directly (10 [14%]), indirectly (49 [66%]), or possibly (15 [20%]) related to Ike. The majority of deaths (n=57) were reported by medical examiners. Deaths occurred in 16 counties of the 44 counties covered by the surveillance. The majority of deaths occurred in Harris and Galveston (28 [38%] and 17 [23%]), respectively. The deceased ranged in age from younger than 1 year to 85 years, with an average age of 46 years (median 50 years); 70% were male. Of the 74 deaths, 47 (64%) resulted from injuries, 23 (31%) from illnesses, and 4 (5%) were undetermined. Among the injuries, carbon monoxide poisoning (13 [18%]) and drowning (8 [11%]) were the leading causes of injury-related deaths. Cardiovascular failure (12 [16%]) was the leading cause of illness-related deaths. 
 
 CONCLUSIONS: 
 
 Defining the relation of death to hurricane using an active mortality surveillance system is possible. The active mortality surveillance form used in Ike provided valuable daily information to DSHS, state emergency management officials, and the CDC regarding the characteristics of deaths in the state. Most of the Ike-related deaths were caused by injury (direct and indirectly related) such as carbon monoxide poisonings and drowning and may have been preventable by educating the public. 
 
 ©2011 American Medical Association. All rights reserved. ||||| Photo courtesy of Kentucky Cabinet for Health and Family Services 
 
 The most important difference between the world today and 150 years ago isn’t airplane flight or nuclear weapons or the Internet. It’s lifespan. We used to live 35 or 40 years on average in the United States, but now we live almost 80. We used to get one life. Now we get two. 
 
 Laura Helmuth Laura Helmuth is the health, science, and environment editor at the Washington Post. From 2012–2016, she was Slate’s science and health editor. Follow her on Twitter. 
 
 You may well be living your second life already. Have you ever had some health problem that could have killed you if you’d been born in an earlier era? Leave aside for a minute the probabilistic ways you would have died in the past—the smallpox that didn’t kill you because it was eradicated by a massive global vaccine drive, the cholera you never contracted because you drink filtered and chemically treated water. Did some specific medical treatment save your life? It’s a fun conversation starter: Why are you not dead yet? It turns out almost everybody has a story, but we rarely hear them; life-saving treatments have become routine. I asked around, and here is a small sample of what would have killed my friends and acquaintances: 
 
 Adrian’s lung spontaneously collapsed when he was 18. 
 
 Becky had an ectopic pregnancy that caused massive internal bleeding. 
 
 Carl had St. Anthony’s Fire, a strep infection of the skin that killed John Stuart Mill.* 
 
 Dahlia would have died delivering a child (twice) or later of a ruptured gall bladder. 
 
 David had an aortic valve replaced. 
 
 Hanna acquired Type 1 diabetes during a pregnancy and would die without insulin. 
 
 Julia had a burst appendix at age 14. 
 
 Katherine was diagnosed with pernicious anemia in her 20s. She treats it with supplements of vitamin B-12, but in the past she would have withered away. 
 
 Laura (that’s me) had scarlet fever when she was 2, which was once a leading cause of death among children but is now easily treatable with antibiotics. 
 
 Mitch was bitten by a cat (filthy animals) and had to have emergency surgery and a month of antibiotics or he would have died of cat scratch fever. 
 
 After a while, these not-dead-yet stories start to sound sort of absurd, like a giddy, hooray-for-modernity response to The Gashleycrumb Tinies. Edward Gorey’s delightfully dark poem is an alphabetical list of children (fictional!) who died gruesome deaths: “A is for Amy who fell down the stairs/ B is for Basil assaulted by bears.” Here’s how modern science, medicine, and public health would amend it: 
 
 M is for Maud who was swept out to sea … then brought back to shore by a lifeguard and resuscitated by emergency medical technicians. 
 
 O is for Olive run through with an awl … but saved during a four-hour emergency surgery to repair her collapsed lung. 
 
 S is for Susan, who perished of fits … or who would have, anyway, if her epilepsy hadn’t been diagnosed promptly and treated with powerful anticonvulsant drugs. 
 
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 Now we’d like to hear your stories. What would have killed you but didn’t? Which friend or relative is alive today thanks to some medical intervention, whether heroic or trivial? Please send your stories to survival_stories@yahoo.com or share them on Twitter using the hashtag #NotDeadYet. We’ll collect the best stories and publish them in Slate next week, at the end of a series of articles about why life expectancy has increased. And congratulations on being alive! 
 
 * * * 
 
 When I first started looking into why average lifespan has increased so much so rapidly, I assumed there would be a few simple answers, a stepwise series of advances that each added a few years: clean water, sewage treatment, vaccines, various medical procedures. But it turns out the question of who or what gets credit for the doubling of life expectancy in the past few centuries is surprisingly contentious. The data are sparse before 1900, and there are rivalries between biomedicine and public health, obstetricians and midwives, people who say life expectancy will rise indefinitely and those who say it’s starting to plateau. 
 
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 It’s important to assign the credit correctly. In much of the developing world, average lifespan hasn’t increased nearly as dramatically as in the United States and the rest of the developed world. (And the United States has a lousy life expectancy compared to other wealthy nations.) Even within the United States, there are huge differences among races, geographic regions, and social classes. Even neighborhoods. These discrepancies are among the greatest injustices of the 21st century. How can we prevent needless premature deaths? What interventions are mostly likely to grant people in poorer countries extra years? And what’s the best way to prolong life and health even further in rich countries? 
 
 Courtesy of Work Projects Administration Poster Collection/Library of Congress 
 
 To understand why people live so long today, it helps to start with how people died in the past. (To take a step back in time, play our interactive game.) People died young, and they died painfully of consumption (tuberculosis), quinsy (tonsillitis), fever, childbirth, and worms. There’s nothing like looking back at the history of death and dying in the United States to dispel any romantic notions you may have that people used to live in harmony with the land or be more in touch with their bodies. Life was miserable—full of contagious disease, spoiled food, malnutrition, exposure, and injuries. 
 
 But disease was the worst. The vast majority of deaths before the mid-20th century were caused by microbes—bacteria, amoebas, protozoans, or viruses that ruled the Earth and to a lesser extent still do. It’s not always clear which microbes get the credit for which kills. Bills of mortality (lists of deaths by causes) were kept in London starting in the 1600s and in certain North American cities and parishes starting in the 1700s. At the time, people thought fevers were spread by miasmas (bad air) and the treatment of choice for pretty much everything was blood-letting. So we don’t necessarily know what caused “inflammatory fever” or what it meant to die of “dropsy” (swelling), or whether ague referred to typhoid fever, malaria, or some other disease. Interpreting these records has become a fascinating sub-field of history. But overall, death was mysterious, capricious, and ever-present. 
 
 The first European settlers to North America mostly died of starvation, with (according to some historians) a side order of stupidity. They picked unnecessary fights with Native Americans, sought gold and silver rather than planting food or fishing, and drank foul water. As Charles Mann points out in his fascinating book 1493: Uncovering the New World Columbus Created, one-third of the first three waves of colonists were gentlemen, meaning their status was defined by not having to perform manual labor. During the winter of 1609–10, aka “the starving time,” almost everyone died; those who survived engaged in cannibalism. 
 
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 Deadly diseases infiltrated North America faster than Europeans did. Native Americans had no exposure and thus no resistance to the common European diseases of childhood, and unimaginable pandemics of smallpox, measles, typhus, and other diseases swept throughout the continent and ultimately reduced the population by as much as 95 percent. 
 
 The slave trade killed more than 1 million Africans who were kidnapped, shackled, and shipped across the Atlantic. Those who survived the journey were at risk of dying from European diseases, as well as starvation and abuse. The slave trade introduced African microbes to North America; malaria and yellow fever were the ones that killed the most. 
 
 Painting by Sidney King/National Park Service/MPI/Getty Images 
 
 Global trade introduced new diseases around the world and caused horrific epidemics until the 1700s or so, when pretty much every germ had made landfall on every continent. Within the United States, better transportation in the 1800s brought wave after wave of disease outbreaks to new cities and the interior. Urbanization brought people into ideal proximity from a germ’s point of view, as did factory work. Sadly, so did public schools: Children who might have toiled in relative epidemiological isolation on farms were suddenly coughing all over one another in enclosed schoolrooms. 
 
 One of the best tours of how people died in the past is The Deadly Truth: A History of Disease in America by Gerald Grob. It’s a great antidote to all the heroic pioneer narratives you learned in elementary school history class, and it makes the Little House on the Prairie books seem delusional in retrospect. Pioneers traveling west in wagon trains had barely enough food, and much of it spoiled; their water came from stagnant, larvae-infested ponds. They died in droves of dysentery. Did you ever play with Lincoln logs or dream about living in a log cabin? What a fun fort for grown-ups, right? Wrong. The poorly sealed, damp, unventilated houses were teeming with mosquitoes and vermin. Because of settlement patterns along waterways and the way people cleared the land, some of the most notorious places for malaria in the mid-1800s were Ohio and Michigan. Everybody in the Midwest had the ague! 
 
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 * * * 
 
 How did we go from the miseries of the past to our current expectation of long and healthy lives? “Most people credit medical advances,” says David Jones, a medical historian at Harvard—“but most historians would not.” One problem is the timing. Most of the effective medical treatments we recognize as saving our lives today have been available only since World War II: antibiotics, chemotherapy, drugs to treat high blood pressure. But the steepest increase in life expectancy occurred from the late 1800s to the mid-1900s. Even some dramatically successful medical treatments such as insulin for diabetics have kept individual people alive—send in those #NotDeadYet stories!—but haven’t necessarily had a population-level impact on average lifespan. We’ll examine the second half of the 20th century in a later story, but for now let’s look at the bigger early drivers of the doubled lifespan. 
 
 The credit largely goes to a wide range of public health advances, broadly defined, some of which were explicitly aimed at preventing disease, others of which did so only incidentally. “There was a whole suite of things that occurred simultaneously,” says S. Jay Olshansky, a longevity researcher at the University of Illinois, Chicago. Mathematically, the interventions that saved infants and children from dying of communicable disease had the greatest impact on lifespan. (During a particularly awful plague in Europe, James Riley points out in Rising Life Expectancy: A Global History, the average life expectancy could temporarily drop by five years.) And until the early 20th century, the most common age of death was in infancy. 
 
 Clean water may be the biggest lifesaver in history. Some historians attribute one-half of the overall reduction in mortality, two-thirds of the reduction in child mortality, and three-fourths of the reduction in infant mortality to clean water. In 1854, John Snow traced a cholera outbreak in London to a water pump next to a leaky sewer, and some of the big public works projects of the late 1900s involved separating clean water from dirty. Cities ran water through sand and gravel to physically trap filth, and when that didn’t work (germs are awfully small) they started chlorinating water. 
 
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 Closely related were technologies to move wastewater away from cities, but as Grob points out in The Deadly Truth, the first sewage systems made the transmission of fecal-borne diseases worse. Lacking an understanding of germs, people thought that dilution was the best solution and just piped their sewage into nearby waterways. Unfortunately, the sewage outlets were often near the water system inlets. Finally understanding that sewage and drinking water need to be completely separated, Chicago built a drainage canal that in 1900 reversed the flow of the Chicago River. The city thus sent its sewage into the greater Mississippi watershed and continued taking its drinking water from Lake Michigan. 
 
 Courtesy of U.S. National Archives and Records Administration 
 
 The germ theory of disease didn’t catch on all that quickly, but once it did, people started washing their hands. Soap became cheaper and more widespread, and people suddenly had a logical reason to wash up before surgery, after defecating, before eating. Soap stops both deadly and lingering infections; even today, kids who don’t have access to soap and clean water have stunted growth. 
 
 Housing, especially in cities, was crowded, filthy, poorly ventilated, dank, stinky, hot in the summer, and cold in the winter. These were terrible conditions to live in as a human being, but a great place to be an infectious microbe. Pretty much everyone was infected with tuberculosis (the main cause of consumption), the leading killer for most of the 19th century. It still has a bit of a reputation as a disease of the young, beautiful, and poetic (it claimed Frederic Chopin and Henry David Thoreau, not to mention Mimì in La Bohème), but it was predominantly a disease of poverty, and there was nothing romantic about it. As economic conditions started improving in the 19th century, more housing was built, and it was airier, brighter (sunlight kills tuberculosis bacteria), more weather-resistant, and less hospitable to vermin and germs. 
 
 We live like kings today—we have upholstered chairs, clean beds, a feast’s worth of calories at any meal, all the nutmeg (people once killed for it) and salt we could ever want. But wealth and privilege didn’t save royalty from early deaths. Microbes do care about breeding—some people have evolved defenses against cholera, malaria, and possibly the plague—but microbes killed off people without regard to class distinctions through the 1600s in Europe. The longevity gap between the rich and the poor grew slowly with the introduction of effective health measures that only the rich could afford: Ipecac from the New World to stop bloody diarrhea, condoms made of animal intestines to prevent the transmission of syphilis, quinine from the bark of the cinchona tree to treat malaria. Once people realized citrus could prevent scurvy, the wealthy built orangeries—greenhouses where they grew the life-saving fruit. 
 
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 Improving the standard of living is one important life-extending factor. The earliest European settlers in North America suffered from mass starvation initially, but once the Colonies were established, they had more food and better nutrition than people in England. During the Revolutionary War era, American soldiers were a few inches taller than their British foes. In Europe, the wealthy were taller than the poor, but there were no such class-related differences in America—which means most people had enough to eat. This changed during the 1800s, when the population expanded and immigrants moved to urban areas. Average height declined, but farmers were taller than laborers. People in rural areas outlived those in cities by about 10 years, largely due to less exposure to contagious disease but also because they had better nutrition. Diseases of malnutrition were common among the urban poor: scurvy (vitamin C deficiency), rickets (vitamin D deficiency), and pellagra (a niacin deficiency). Improved nutrition at the end of the 1800s made people taller, healthier, and longer lived; fortified foods reduced the incidence of vitamin-deficiency disorders. 
 
 Photo courtesy of New York Public Library Archives/Tucker Collection 
 
 Contaminated food was one of the greatest killers, especially of infants; once they stopped breast-feeding, their food could expose them to typhoid fever, botulism, salmonella, and any number of microbes that caused deadly diarrhea in young children. (Death rates for infants were highest in the summer, evidence that they were dying of food contaminated by microbes that thrive in warm conditions.) Refrigeration, public health drives for pure and pasteurized milk, and an understanding of germ theory helped people keep their food safe. The Pure Food and Drug Act of 1906 made it a crime to sell adulterated food, introduced labeling laws, and led to government meat inspection and the creation of the Food and Drug Administration. 
 
 People had started finding ways to fight disease epidemics in the early 1700s, mostly by isolating the sick and inoculating the healthy. The United States suffered fewer massive epidemics than Europe did, where bubonic plague (the Black Death) periodically burned through the continent and killed one-third of the population. Low population density prevented most epidemics from becoming widespread early in the United States history, but epidemics did cause mass deaths locally, especially as the population grew and more people lived in crowded cities. Yellow fever killed hundreds of people in Savannah in 1820 and 1854; the first devastating cholera epidemic hit the country in 1832. Port cities suffered some of the worst outbreaks because sailors brought new diseases and strains with them from all over the world. Port cities instituted quarantines starting in the 19th century, preventing sailors from disembarking if there was any evidence of disease, and on land, quarantines separated contagious people from the uninfected. 
 
 A smallpox epidemic in Boston in 1721 led to a huge debate about variolation, a technique that involved transferring pus from an infected person to a healthy one to cause a minor reaction that confers immunity. Rev. Cotton Mather was for it—he said it was a gift from God. Those opposed said that disease was God’s will. People continued to fight about variolation, then inoculation (with the related cowpox virus, introduced in the late 1700s), and finally vaccination. The fight over God’s will and the dangers of vaccinations (real in the past, imaginary today) are still echoing. 
 
 In the early 1900s, antitoxins to treat diphtheria and vaccines against diphtheria, tetanus, and pertussis helped stop these deadly diseases, followed by vaccines for mumps, measles, polio, and rubella. 
 
 Anne Schuchat, assistant surgeon general and the acting director of CDC's Center for Global Health, says it’s not just the scientific invention of vaccines that saved lives, but the “huge social effort to deliver them to people improved health, extended life, and kept children alive.” Vaccines have almost eliminated diseases that used to be common killers, but she points out that “they’re still circulating in other parts of the world, and if we don’t continue to vaccinate, they could come back.” 
 
 Courtesy of Sandra W. Roush, Trudy V. Murphy, and the Vaccine-Preventable Disease Table Working Group/Journal of the American Medical Association 
 
 Vaccines have been so effective that most people in the developed world don’t know what it’s like to watch a child die of pertussis or measles, but parents whose children have contracted these diseases because of anti-vaccine paranoia can tell them. “The mistake that we made was that we underestimated the diseases and we totally overestimated the adverse reactions [to vaccines]," says a father in New Zealand whose child almost died of an agonizing bout of tetanus. 
 
 Schuchat says the HPV vaccine is a huge priority now; only one-third of teenage girls have received the full series of three shots required to protect them against viruses that cause cervical cancer. The vaccines “are highly effective and very safe, but our uptake is horrible. Thousands of cases of cervical cancer will occur in a few decades in people who are girls now.” 
 
 Photo by Keystone Features/Getty Images 
 
 Some credit for the historical decrease in deadly diseases may go to the disease agents themselves. The microbes that cause rheumatic fever, scarlet fever, and a few other diseases may have evolved to become less deadly. Evolutionarily, that makes sense—it’s no advantage to a parasite to kill its own host, and less-deadly strains may have spread more readily in the human population. Of course, sudden evolutionary change in microbes can go the other way, too: The pandemic influenza of 1918–19 was a new strain that killed more people than any disease outbreak in history—around 50 million. In any battle between microbes and mammals, the smart money is on the microbes. 
 
 Over the next week, we’ll take a closer look at deaths in childbirth and changes in life expectancy in adulthood. We’ll examine the evolution of old age and the social repercussions of having infants that survive and a robust population of old people, and we’ll list some of the oddball, underappreciated innovations that may have saved your life. In the meantime, please play the Wretched Fate game and send us your #NotDeadYet survival stories on Twitter or survival_stories@yahoo.com. 
 
 Please read the rest of Laura Helmuth's series on longevity, and play our "Wretched Fate" interactive game to learn how you would have died in 1890.
– In a piece last week on Slate, Laura Helmuth took a long and interesting look at what she dubs "the most important difference between the world today and 150 years ago": the doubling of our lifespan, from about 40 years to about 80. She looked at the big reasons why, of which you probably could come up with a few—like vaccines, clean water, refrigeration. But Helmuth's fascinating follow-up piece takes things a step further, and her headline says it all: "Fourteen Oddball Reasons You're Not Dead Yet." Here are our favorite four: Cotton: Before we started wearing cotton we wore wool, which was tougher to clean. That made it a more welcoming home for body lice, which spread one of history's big killers: typhus. Satellites: Helmuth is referring to the weather-observing kind, which alert us to hurricanes with enough time to prepare and, importantly, evacuate. To wit, she cites a 1900 hurricane that killed 8,000 in Galveston. Hurricane Ike brought a higher storm surge in 2008, but the Texas Department of State Health Services identified just 74 deaths. Window screens: They keep out houseflies, and that has saved us from more than just some hand-swatting. Though Helmuth acknowledges that clean water and sewage treatment were the biggest factors in squashing the spread of potentially fatal diarrhea, flies were also a vector. Shoes: If you think disease-carrying flies sound gross, well, meet hookworms. These parasites find their way from the feces of an infected person (which were ostensibly on the ground) and into the body of another person through the feet. They did so frequently in the Southeast before wearing shoes became an encouraged practice. Head to Slate for the other 10 items on her list, which includes the residents of Framingham, Mass.