Evolving an arch across the foot’s width helped hominids walk upright
The arch running across the width of the human foot might be a big part of the reason that people can walk and run upright, a new study suggests. People have a prominent arch along the insides of their feet from ball to heel — a structure that helps make feet stiff to withstand forces on the foot caused by walking and running. But there’s another, less obvious arch. Bones in the middle of the foot, called metatarsals, are arranged in a curve across the foot’s width. This bend, called the transverse tarsal arch, stiffens the foot lengthwise and may have evolved more than 3.4 million years ago, a step toward ancient hominids gaining the ability to walk and run on two feet unlike other primates, researchers report February 26 in Nature. Scientists knew that the arch on the inside of the foot, called the longitudinal arch, makes the foot more rigid, thanks to the arch’s shape and elastic tissues...