Wearing shoes when we walk changes how our feet interact with the ground below us, according to a novel new study in the journal Nature of shod and unshod walkers, the state of their feet and the extent of the forces they generate with every step.

The study, which echoes some of the research that first popularized barefoot running, finds that walkers move differently when they are barefoot or shod and have differing sensitivity to the ground, potentially affecting balance and joint loading. The results intimate that there could be advantages to perambulating with naked feet, not the least of which, surprisingly, involves developing calluses.

We humans are born to walk. Distance running during hunts may have been important for the survival of early homo sapiens, most evolutionary biologists agree. But our forebears almost certainly spent far more time walking than jogging, just as modern hunter-gatherers do.

Shoes, though, are new to us. Archaeological finds indicate that humans first started wearing rudimentary sandals about 40,000 years ago, an eyeblink in our history as a species. Before then, nature seems to have deemed that our best protection for bare feet would be tough skin. So, people who walk without shoes develop hard, leathery calluses on the heels and balls of their feet that can reduce sensations of pain when they stride over small obstacles like gravel.