One of the pleasures of Scientific American, I’ve always thought, is that it offers armchair travelers a vicarious expedition to the exciting worlds uncovered through science. I reflected on that fact recently as I sat on the tarmac, my flight 23rd in line for takeoff at LaGuardia Airport in New York City. I was reading over this issue’s articles and again became absorbed by our cover story, “The First Americans,” by Heather Pringle. Time rolled back in my mind’s eye, and I imagined a wholly different journey than the one I was taking.

What might it have been like to step across Beringia, the bridge between Asia and the Americas, during the last ice age? You are wearing warm, tailored clothing of hides, stitched together with bone needles. You are expert at reading the land for clues about the presence of prey and edible vegetation. Massive ice sheets cover much of your Arctic world. One day, ahead of you, you see a grassy plain—the dry winds whistling across it have made snowfall scant. Behind you are campfires, but none lie ahead. Drawn by the open path and the promise of richer hunting, you step toward a New World.

Studies of genetics and the recently discovered trove of more than 19,000 stone tools and other evidence from 15,500 years ago are helping scientists piece together those trailblazers’ paths and what their lives were like. The findings indicate that humans arrived thousands of years earlier than previously thought.

Other science excursions in this issue include going to the Red Planet (“Digging Mars”), to Central America and elsewhere to battle dengue (“The Wipeout Gene”), and to the frontiers of medicine (“The Medical Sleuth”).

As for me, I was headed to Washington, D.C., where we held a reception with policy leaders on Capitol Hill to celebrate the magazine’s September single-topic issue on cities. Joining me was Harvard University economist Edward Glaeser, author of two pieces, who spoke about how, done right, with an emphasis on education, the greater density of humanity afforded by urban living can help us innovate our way out of the problems facing us today. That’s a journey we’ll all be making together.