Early on, Clarke became an expert in phylogenies, or evolutionary trees, and has produced more than a dozen papers organizing and reorganizing these trees using data from fossilized bones from around the world. But when one studies the relationships among dinosaur fossils, one can’t help but fill in muscles and soft tissue. So, not surprisingly, Clarke soon became fascinated with how the bird-dinosaurs moved.
When Clarke talks about evolution, the adaptations that separate one animal from another on her phylogenic trees, she often sounds as if she’s describing a Silicon Valley start-up. Every change that led to flight is an “innovation” in her parlance. In some sense, that’s what she’s dedicated her life to – the study of animal innovation.
So what led to one of the greatest innovations in the history of life on the planet? What in the dinosaur body led to flying birds? Certainly, movement and body design are at the top of the list. Clarke has looked at the earliest examples of the fan-like tail that flying dinosaurs used to stay stable in the air as well as the size of the animal – consistently small-framed. She also helped overturn the commonly repeated supposition that feathers arose to power flight. Far from it, in fact: rudimentary feathers existed 100 million years before flight, during the early days of dinosaurs.
“Feathers evolved for some other purpose,” Clarke says. “There’s an independent event that led to diversification in body coverings that has nothing to do with flight. It has to do with changes in locomotion in a different, earlier period close to the start of the age of dinosaurs.”