The Origin Of Wings

The ancestors of birds may have evolved wings not for flying but for running faster, a study suggests.

The study might answer a key question about the origin of bird flight.

Many scientists believe birds descended from two-legged dinosaurs like Velociraptor, featured in Jurassic Park. The problem has been explaining how the clawed dinosaur forelimbs developed into the wings of the first known bird, Archaeopteryx, which lived 140 million to 150 million years ago.

Some of these dinosaurs must have had limbs that resembled wings, but not enough to allow them to fly. If they couldn't fly with them, why have them?

Paleontologist Luis M. Chiappe of the Natural History Museum of Los Angeles County and aerodynamic engineer Phillip Burger of the San Diego Natural History Museum think they have found the answer.

They believe the crow-sized Archaeopteryx took off from the ground. But it appeared too weak to launch itself from a standing start, as most modern birds can, and too slow to gain lift from just running.

So how did it get into the air? In Thursday's issue of the journal Nature, Chiappe and Burger calculate that Archaeopteryx could almost quadruple its running speed with thrust from flapping its wings.

They estimate with a runway of 10 to 15 yards, it could achieve the 18-mph takeoff speed in about three seconds.

Flightless ancestors of Archaeopteryx could have used rudimentary wings to speed up when chasing prey or escaping predators, Chiappe said.

However, the theory does not fly with paleo-ornithologist Larry Martin of the University of Kansas at Lawrence.

Â"If you could increase your ground speed by flapping your wings, then I suppose birds that run on the ground would do this. As far as I know, there is no modern bird that flaps its wings to increase its ground speed,Â" he said. Â"I grew up on a farm. I've chased chickens. I know that when they get their wings out, it's about when they're ready to fall they use it as balance. But I've never seen one flap its wings with the idea of increasing its speed.Â"

Chiappe disagreed.

Â"If you go to a chicken farm and chase a chicken very closely, the chicken will start flapping its wings and it will run faster,Â" he said.

Martin and some other scientists favor the idea that Archaeopteryx and its immediate ancestors lived in trees and started flying by jumping off branches. The wings of its predecessors, if not good enough for flying, could have helped in gliding.