...While the evolution from the Neolithic solid stone wheel with a single hole for an axle 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 and quicker over millions of years on Earth, according to a Duke University engineer.

Adrian Bejan, professor of mechanical engineering at Duke's Pratt School of Engineering, argues that just as the design of wheels became lighter with fewer spokes over time, and better at distributing the stresses of hitting the ground, animals have evolved as well to move better on Earth. In essence, over millions of years, animals such as humans developed the fewest "spokes," or legs, as the most efficient method for carrying an increasing body weight and height more easily.

Bejan's analysis was published early online in the American Journal of Physics. His research is supported by the National Science Foundation and the Air Force Office of Scientific Research....