In the winter of 2013 I set out from an ancient Homo sapiens fossil site called Herto Bouri, in the north of Ethiopia, and began retracing, on foot, the defining journey of humankind: our first colonization of the Earth during the Stone Age.

My long walk is about storytelling. I report what I see at boot level along the pathways of our original discovery of the planet. From the start, I knew my route would be vague. Anthropologists suggest that our species first stepped out of Africa 600 centuries ago and eventually wandered, more or less aimlessly, to the tip of South America—the last unknown edge of the continents and my own journey’s finish line. We were roving hunters and foragers.