Starting with the foot, DeSilva held up a cast with 26 bones and said: "You wouldn’t design it out of 26 moving parts." Our feet have so many bones because our ape-like ancestors needed flexible feet to grasp branches. But as they moved out of the trees and began walking upright on the ground in the past 5 million years or so, the foot had to become more stable, and bit by bit, the big toe, which was no longer opposable, aligned itself with the other toes and our ancestors developed an arch to work as a shock absorber. "The foot was modified to remain rigid," said DeSilva. "A lot of BandAids were stuck on these bones." But the bottom line was that our foot still has a lot of room to twist inwards and outwards, and our arches collapse. This results in: ankle sprains, plantar fasciitis, Achilles tendonitis, shin splints, and broken ankles. These are not modern problems, due to stiletto heels; Fossils show broken ankles that have healed as far back as 3 million years ago.

A better design for upright walking and running, DeSilva said, would be a foot and ankle like an ostrich. An ostrich’s ankle and lower leg bones are fused into a single structure, which puts a kick into their step—and their foot has only two toes that aid in running. "Why can’t I have a foot like that?" asked DeSilva. One reason is that ostriches trace their upright locomotion back 230 million years to the age of dinosaurs, while our ancestors walked upright just 5 million years ago.

Turning up the pain threshold a notch, anatomist and paleoanthropologist Bruce Latimer of Case Western Reserve University in Cleveland, Ohio, limped to the podium, dangling a twisted human backbone as evidence of real pain. "If you want one place cobbled together with duct tape and paper clips it’s the back," said Latimer, a survivor of back surgery.