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"Wheel Deal" -- The Discovery Files

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While the evolution from the Neolithic stone wheel to the sleek wheels of today's racing bikes can be seen as the result of human ingenuity, it also represents how animals, including humans, have come to move more efficiently over millions of years on Earth, according to a Duke University engineer.

Credit: NSF/Karson Productions

Audio Transcript:

Walk 'n Roll.

I'm Bob Karson with the discovery files -- new advances in science and engineering from the National Science Foundation.

How is a living creature like a wheel? That's the basis of an analysis by mechanical engineering professor Adrian Bejan at Duke University. He looked at the continuing evolution of human and animal movement but with a 'wheel' twist.

(Sound effect: rolling stone wheel) Early wheel -- solid stone, hole for an axle -- heavy -- the stresses of hitting the ground not evenly distributed. (Sound effect: wagon wheels) Subsequent generations of wheels on wagons and carriages became lighter and better at distributing stresses, by using tens of spokes. Fast-forward to today's racing bikes -- (Sound effect: racing bike) lightweight, strong, uniform stress distribution but with only a few spokes needed to do the job.

According to Bejan, it's the same in nature. Over millions of years, animals -- including humans -- developed the fewest "spokes," or legs, to efficiently carry increasing body weight and height. Bejan says that we are really both a wheel and a vehicle for movement -- a 'rolling' body. (Sound effect: runner) Our two legs swinging back and forth act like one wheel with two spokes.

Bejan believes these changes in wheel and animal movement are predictable according to his constructal theory of design: for a design to persist in time, it must evolve to move more freely through its environment.

Understanding mobility in this context may be a 'wheel' breakthrough.

"The Discovery Files" covers projects funded by the government's National Science Foundation. Federally sponsored research -- brought to you, by you! Learn more at or on our podcast.

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