The Places In Between
Stewart's walk through Afghanistan was part of a larger trek that included 16 months of walking 20 to 25 miles a day across Iran, Pakistan, India and Nepal.
All of which makes him an expert on walking. But don't take my word for it. Here's a passage from The Places In Between:
I thought about evolutionary historians who argued that walking was a central part of what it meant to be human. Our two-legged motion was what first differentiated us from the apes. It freed our hands for tools and carried us on the long marches out of Africa. As a species, we colonized the world on foot. Most of human history was created through contacts conducted a walking pace....And Stewart thought these thoughts — of course — while walking!