How did some feathered dinosaurs begin to fly?
Dinosaurs needed more than just feathers to fly. They had to evolve the special arrangement of bones and muscles that makes it possible for birds to flap their wings. Traditionally, paleontologists have put forward alternative scenarios in which flight evolved either from the trees down or the ground up. In the trees-down scenario, tree-climbing dinosaurs jumped to the ground or to other trees, and feathers on their outstretched forelimbs helped extend their fall. Eventually their descendants became gliders, and then finally they began to flap their wings. In the ground-up scenario, small theropods somehow evolved a flight stroke even while they were adapted for running on the ground—perhaps by grabbing prey with their hands. “This was a false dichotomy,” says Hans-Dieter Sues. In recent years, for example, scientists have discovered some very small feathered theropods that may have been able to climb trees. Meanwhile, Ken Dial of the University of Montana has found that partridges can
