Origin of human bipedalism is studied

ST. LOUIS, July 17 (UPI) -- U.S. anthropologists believe they have confirmed the theory that early humans began walking on two legs as a way to reduce locomotor energy costs.

The researchers, in what is believed the first study to fully examine the theory, found human walking is approximately 75 percent less costly in terms of energy and caloric expenditure than is quadrupedal and bipedal walking in chimpanzees.

The scientists posit that energy savings provided early hominids with an evolutionary advantage over other apes by reducing the cost of foraging for food.

Researchers led by Assistant Professor Herman Pontzer at Washington University in St. Louis, in collaboration with Michael Sokol of the University of California-Davis and David Raichlen of the University of Arizona , used treadmill trials to analyze walking energetics and biomechanics of adult chimpanzees and humans.

The team also examined the early hominid fossil record, which they found to include predicted changes consistent with lower energy cost -- longer hind legs compared with body mass and structural changes to the pelvic bone allowing for more upright walking.

The research appears online in the Proceedings of the National Academy of Sciences.