A study of humans and chimpanzees has provided new evidence to support the theory that our ancestors evolved to walk upright for the simple reason that doing so saves energy.

The study, which used treadmills, shows that people walking on two legs use 25% of the energy used by chimps who "knuckle walk" on all fours. Researchers hope that future fossil findings will reveal the precise anatomical changes that enabled our ancestors to take up bipedalism.

heh. I can't wait till gym trainers convince people that they'll loose 4 times as much weight if they walk like a monkey on the tread mill. I want pictures.