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02/15/2013

Hey human - bet you wish you had ostrich feet

Hey human. You, with the extra large head. The one walking on two feet. I bet you think you're pretty well adapted. Any primate at the apex of the global food chain must be, right?

Not so fast.

The same traits that set humans on a separate evolutionary pathway from our primate cousins -- extra large craniums to fit our extra large brains, upright postures and walking on two feet, long lifespans and high fertility -- left evolutionary scars that mar humans to this day. Or so a panel of scientists at the AAAS annual meeting in Boston told a large and increasingly broken-down feeling crowd.

Take the foot. The ability to walk on two feet rather than four was a crucial adaptation associated with early humans moving out of the forest. But it means that given only a few million years of evolutionary lead time, an appendage adapted to swinging through forests does not do a great job at supporting an upright human, said Boston University's Jeremy DeSilva.

"Human feet are simply modified ape feet," he said. From an engineering stand point, they are "26 moving parts fused together with biological equivalent of duct tape and paper clips."

He compared humans to another bipedal animal, the ostrich. Ostriches have fused ankles, single tendons that run down the entire leg, and muscles inside the body cavity, giving them extra kick.

"Why can't I have a foot like that?" asked DeSilva.

He pointed out that efficiently designed prosthesis, like those used by Oscar Pistorius (whose legal troubles are now rapidly eclipsing his athletic achievements) look nothing like human legs and feet -- in fact, they look like ostriches'.

But "birds have a 230-million year headstart on us," he said: they evolved from bipedal dinosaurs. Humans evolved from quadropedal mammals. Hence the stratospheric success of the orthopedic industry, DeSilva suggested.

Kate Allen is the Star's global science and technology reporter. She is reporting from the AAAS meeting in Boston this week. Follow her on Twitter @katecallen

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