For more than a century, scientists have wondered how Archaeopteryx, one of the earliest known birds, managed to get off the ground.
A new study suggests the answer may have been surprisingly simple: it jumped several times using its powerful legs while its wings helped it build enough speed to fly.
Researchers at the University of Southampton used computer modeling and observations of modern birds to reconstruct how Archaeopteryx may have taken flight about 150 million years ago.
Archaeopteryx holds an important place in evolutionary history because it combined features of both dinosaurs and birds.
It had feathers and wings, but it also retained dinosaur-like characteristics, including teeth, claws on separate fingers and a long, bony tail.
Its flight equipment was also much less developed than that of modern birds.
Today’s birds can usually launch themselves into the air with one powerful jump followed by rapid wingbeats. Archaeopteryx faced some major limitations. Its shoulder joints had restricted movement, and it lacked the large, keeled breastbone that provides an attachment point for the powerful flight muscles of modern birds.
These limitations meant Archaeopteryx probably could not simply jump once and immediately fly away.
Scientists have proposed several other possibilities over the years. Perhaps early birds ran up slopes while flapping their wings, or maybe they climbed trees or cliffs and glided downward. But testing these ideas with an animal that disappeared millions of years ago is extremely difficult.
For the new study, researchers took a different approach. They combined detailed computer models with observations of living birds, including gulls, crows, magpies and finches. They then adjusted the models to match the anatomy of Archaeopteryx.
The researchers examined how much force the ancient bird’s hips, knees and ankles could produce and estimated the speed it needed to remain in the air.
Their results suggest the legs played the crucial role.
A medium-sized Archaeopteryx weighing about 400 grams could have reached a sustainable flight speed of around 7 meters, or 23 feet, per second after three jumps. Alternatively, it could have achieved the necessary speed with two jumps if it added a downward wing flap between them.
In other words, Archaeopteryx may have launched itself with a sequence resembling jump, jump, jump and then flight—or jump, flap, jump and fly.
The idea has parallels in birds living today. Although modern birds are capable of taking off with a single powerful leap, many species use several hops when they are not in a hurry. Crows, magpies and seagulls, for example, can use this energy-saving strategy.
Leg power remains surprisingly important even in modern bird flight. According to the researchers, as much as 90% of the force needed to initially leave the ground can come from the legs before the wings take over.
The findings suggest that strong hind legs may have provided an important evolutionary bridge between running dinosaurs and the highly capable flying birds we see today.
