I went recently to San Francisco to give a talk to a conference of scientists. The scientists were experts in gathering together mountains of biological data—genome sequences, results of experiments and clinical trials—and figuring out how to make them useful: turning them into new diagnostic tests, for example, or a drug for cancer. The invitation was an honor, but a nerve-wracking one. As a journalist, I had no genome scan to offer the audience. We science writers do have one ace in the hole, though. Instead of being lashed to a lab bench for years, carrying out experiments to illuminate...