The French biologist Jacques Monod once famously said, "What is true for E. coli is true for the elephant." At the time, he was referring to the universal rules of molecular biology--of DNA and proteins, for example, that are the same from one species to another. As scientists in the mid-1900s figured out the workings of E. coli, they were also figuring out the workings of life in general. In my new book Microcosm, I make the case that Monod's words were more true than even he realized. In the Boston Globe today, I explain how scientists used to think that there was one big difference between E. coli and the elephant (and us)--we get old and E. coli doesn't. But now it turns out that E. coli was not immortal after all. And that discovery means that E. coli may help reveal secrets about Alzheimer's disease and other burdens of old age. Read it here.