Lifespan has doubled in the United States in the past 150 years. This ridiculously wonderful change is something we tend to take for granted. When we do think about why we're living longer, some of the fairly obvious reasons include vaccines, antibiotics, clean water, or drugs for heart disease and cancer. But the world is full of underappreciated innovations that also save lives. Here's a list of 10 of them.

Cotton. One of the major killers in human history was typhus, a bacterial disease spread by lice. It defeated Napoleon's army. Wool was the clothing material of choice before cotton displaced it. Cotton is easier to clean and less hospitable to body lice.

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. This time we saw it coming, thanks to a network of satellites. More than 100 people died, but more than 1 million evacuated 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 fluoridated water.

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 until the 1920s, when 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. Double-blind trials overcome these biases.

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.

Air-conditioning. Heat is deadly and we don't respect it enough. 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, which is still going strong and now includes the children and grandchildren of the original cohort. 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 commitment of such volunteers, we know the dangers of high cholesterol, obesity, inactivity and smoking.

Shoes. Hookworms are parasites that enter the human body through bare feet - often by biting into the soft skin between the toes. The disease was common in the Southeast until education initiatives encouraged people to build sanitary outhouses and wear shoes.

Cows. The Midwest once had some of the worst malaria outbreaks in the country. Mosquitoes flourish in the damp lowlands, and settlers' farming practices made for even more stagnant water. 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.

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.

Laura Helmuth is Slate's science and health editor.

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