A tiny winged robot, weighing less than a bar of chocolate, has led a group of scientists to believe that avian flight evolved from tree-dwelling animals.
The six legged, 25-gram 'DASH+Wings' bot was put through a series of mini Olympic events by engineers at the University of California, to help solve evolutionary flight questions.
Around 150million years ago, dinosaurs like Archaeopteryx were flying around the forest. But how animals developed these primitive wings before bird ancestors could fly was unknown.
There are two schools of thought on the subject. The 'trees-down' theory suggests primitive wings enabled creatures to glide down from trees - in the same way as a flying squirrel.
The 'ground-up' theory suggests avian ancestors used their wings to 'run flap' along the floor, making it easier to run up inclines and making them faster.
The latter is problematic due to the huge speeds required for liftoff, but, gliding improvements could have led to flight.
The bot was made to scamper up a steep incline with flapping wings but performed best with them when gliding:
Fossil evidence hasn't thrown up much for scientists to go on, but the results from DASH+Wings could go some way towards settling the matter.
University of California engineers Ronald Fearing and Kevin Peterson and paleobiologist Robert Dudley, made their mini robot run as fast as it could across the floor and up increasingly steep ramps.
They also made it jump from a platform and glide as far as possible.
For each event the robot performed with wings and then without, with them flapping and then without. Having a pair of flapping wings helped for every test, but proved most effective for gliding.
Flapping wings allowed the bot to increase its running speed, but only by 90 per cent rather than the 400 per cent needed, in theory, for flight.
But gliding with flapping wings enabled it to sail farther than when its wings were still.
'This result lends indirect support to the theory that avian flight evolved from tree-dwelling animals and not from land animals that required ground-based running takeoffs,' Mr Peterson said.
But, others are not so convinced.
Brandon Jackson, an evolutionary biologist at the University of Montana, told Science Magazine the results supported the gliding theory, but wouldn't rule out the ground-up theory.
'This study is a beautiful example of how relatively simple bioinspired robots can address [questions] that are difficult or impossible to test in living organisms,' Professor Jackson said.
'The question of avian flight origins is far from answered.'
The study is published in the journal Bioinspiration & Biomimetics. <iframe width="480" height="360" src="http://www.youtube.com/embed/4V1631-Vcm4" frameborder="0" allowfullscreen></iframe>
