George Johnson writes about a recent study that concluded that most cancer is caused by random mutations rather than environment or heredity. This is good news and bad news: your behavior makes less difference than you think. Smoking is obviously bad, but otherwise your behavior and genes only have a minority effect on your cancer risk.
Some of these genetic misprints are caused by outside agents, chemical or biological, especially in parts of the body -- the skin, the lungs and the digestive tract -- most exposed to the ravages of the world. But millions every second occur purely by chance -- random, spontaneous glitches that may be the most pervasive carcinogen of all.
It's a truth that grates against our deepest nature. That was clear earlier this month when a paper in Science on the prominent role of "bad luck" and cancer caused an outbreak of despair, outrage and, ultimately, disbelief.
The most intemperate of this backlash -- mini-screeds on Twitter and hit-and-run comments on the web -- suggested that the authors, Cristian Tomasetti and Bert Vogelstein of Johns Hopkins University, must be apologists for chemical companies or the processed food industry. In fact, their study was underwritten by nonprofit cancer foundations and grants from the National Institutes of Health. In some people's minds, those were just part of the plot.
What psychologists call apophenia -- the human tendency to see connections and patterns that are not really there -- gives rise to conspiracy theories. It is also at work, though usually in a milder form, in our perceptions about cancer and our revulsion to randomness.
You can view cancer like a slow-motion car crash: most of the time it's not your fault, and it really sucks. Unlike a fatal car crash, cancer usually gives you time to see your loved ones.