Two small genetic changes reshaped the human pelvis, setting our early ancestors on the path to upright walking, scientists say.
One genetic change flipped the ilium — the bone your hands rest on when you put them on your hips — 90 degrees. The rotation reoriented the muscles that attach to the pelvis, turning a system for climbing and running on all four legs into one for standing and walking on two legs. The other change delayed how long it takes for the ilium to harden from soft cartilage into bone, evolutionary biologist Gayani Senevirathne of Harvard University and colleagues report in the Sept. 25 Nature. The result: a