The birth of birds

摘要

It took a lot to turn lumbering cousins of Tyrannosaurus rex into agile hummingbirds and graceful swans. This year, evolutionary biologists figured out the mode and tempo of the spectacular evolutionary transition from dinosaurs to birds. Their analyses top off 2 decades of fossil discoveries, primarily in China, showing that birdlike innovations-particularly feathers-emerged repeatedly among dinosaurs, well before the first birds appeared. Feathers, it seems, were not just for flying, but also for insulation, display, or possibly balance.