This is the message of a paper by Tomasetti and Vogelstein, that came out last week. Unlike a lot of papers in Science it is beautifully written, with a simple idea and a clear message. They start with the simple observation that some cancers are much much more common than others. For example, the American figures they quote give a lifetime risk of cancer of the colon of 5%, and risk of bone cancer of the pelvis of 0.0003%. Why the difference?