That Daily Shower Can Be a Killer By JARED DIAMOND The other morning, I escaped unscathed from a dangerous situation. No, an armed robber didn't break into my house, nor did I find myself face to face with a mountain lion during my bird walk. What I survived was my daily shower. You see, falls are a common cause of death in older people like me. (I'm 75.) Among my wife's and my circle of close friends over the age of 70, one became crippled for life, one broke a shoulder and one broke a leg in falls on the sidewalk. One fell down the stairs, and another may not survive a recent fall. "Really!" you may object. "What's my risk of falling in the shower? One in a thousand?" My answer: Perhaps, but that's not nearly good enough. Life expectancy for a healthy American man of my age is about 90. (That's not to be confused with American male life expectancy at birth, only about 78.) If I'm to achieve my statistical quota of 15 more years of life, that means about 15 times 365, or 5,475, more showers. But if I were so careless that my risk of slipping in the shower each time were as high as 1 in 1,000, I'd die or become crippled about five times before reaching my life expectancy. I have to reduce my risk of shower accidents to much, much less than 1 in 5,475. This calculation illustrates the biggest single lesson that I've learned from 50 years of field work on the island of New Guinea: the importance of being attentive to hazards that carry a low risk each time but are encountered frequently. I first became aware of the New Guineans' attitude toward risk on a trip into a forest when I proposed pitching our tents under a tall and beautiful tree. To my surprise, my New Guinea friends absolutely refused. They explained that the tree was dead and might fall on us. Yes, I had to agree, it was indeed dead. But I objected that it was so solid that it would be standing for many years. The New Guineans were unswayed, opting instead to sleep in the open without a tent. I thought that their fears were greatly exaggerated, verging on paranoia. In the following years, though, I came to realize that every night that I camped in a New Guinea forest, I heard a tree falling. And when I did a frequency/risk calculation, I understood their point of view. Consider: If you're a New Guinean living in the forest, and if you adopt the bad habit of sleeping under dead trees whose odds of falling on you that particular night are only 1 in 1,000, you'll be dead within a few years. In fact, my wife was nearly killed by a falling tree last year, and I've survived numerous nearly fatal situations in New Guinea. I now think of New Guineans' hypervigilant attitude toward repeated low risks as "constructive paranoia": a seeming paranoia that actually makes good sense. Now that I've adopted that attitude, it exasperates many of my American and European friends. But three of them who practice constructive paranoia themselves — a pilot of small planes, a river-raft guide and a London bobby who patrols the streets unarmed — learned the attitude, as I did, by witnessing the deaths of careless people. Traditional New Guineans have to think clearly about dangers because they have no doctors, police officers or 911 dispatchers to bail them out. In contrast, Americans' thinking about dangers is confused. We obsess about the wrong things, and we fail to watch for real dangers. Studies have compared Americans' perceived ranking of dangers with the rankings of real dangers, measured either by actual accident figures or by estimated numbers of averted accidents. It turns out that we exaggerate the risks of events that are beyond our control, that cause many deaths at once or that kill in spectacular ways — crazy gunmen, terrorists, plane crashes, nuclear radiation, genetically modified crops. At the same time, we underestimate the risks of events that we can control ("That would never happen to me — I'm careful") and of events that kill just one person in a mundane way. Having learned both from those studies and from my New Guinea friends, I've become as constructively paranoid about showers, stepladders, staircases and wet or uneven sidewalks as my New Guinea friends are about dead trees. As I drive, I remain alert to my own possible mistakes (especially at night), and to what incautious other drivers might do. My hypervigilance doesn't paralyze me or limit my life: I don't skip my daily shower, I keep driving, and I keep going back to New Guinea. I enjoy all those dangerous things. But I try to think constantly like a New Guinean, and to keep the risks of accidents far below 1 in 1,000 each time. Jared Diamond, a professor of geography at the University of California, Los Angeles, is the author of the new book "The World Until Yesterday: What Can We Learn From Traditional Societies?"