Ever since Mary Higby Schweitzer peeked inside the fractured thighbone of a Tyrannosaurus rex the introverted scientist's life hasn't been the same. Neither has the field of paleontology.
Two years ago, Schweitzer gazed through a microscope in her laboratory at North Carolina State University and saw lifelike tissue that had no business inhabiting a fossilized dinosaur skeleton: fibrous matrix, stretchy like a wet scab on human skin; what appeared to be supple bone cells, their three-dimensional shapes intact; and translucent blood vessels that looked as if they could have come straight from an ostrich at the zoo.
By all the rules of paleontology, such traces of life should have long since drained from the bones. It's a matter of faith among scientists that soft tissue can survive at most for a few tens of thousands of years, not the 65 million since T. rex walked what's now the Hell Creek Formation in Montana. But Schweitzer tends to ignore such dogma. She just looks and wonders, pokes and prods, following her scientific curiosity. That has allowed her to see things other paleontologists have missed—and potentially to shatter fundamental assumptions about how much we can learn from the past. If biological tissue can last through the fossilization process, it could open a window through time, showing not just how extinct animals evolved but how they lived each day. "Fossils have richer stories to tell—about the lub-dub of dinosaur life—than we have been willing to listen to...