It is night. I hear Mohamad Banounah praying: “. . . بسم الله الرحمان الرحيم . . . ”

He is bent at the waist, circling my sleeping bag, walking backward through the dark. Is it a joke? Some type of dance? Is he suffering from heatstroke? No: It is an improvised blessing. My Saudi guide, a compact, effusive, methodical man, a desert survival expert, a wildlife photographer, a retired military officer, is dragging a stick through the sand. He is drawing a circle around my tarp—invoking the name of Allah, the Benificent, the Merciful, for divine protection. It is our first camp in the desert of Arabia.

We have walked two days out of the vast port city of Jeddah: more than 60 miles atop sidewalks sterilized by the cauterizing rays of the sun. Behind us: the jostling dreams of 3.5 million slumbering urbanites. Ahead: the long, austere, salt plain of the Hejaz coast, a white ramp that leads 700 miles north to Jordan—a strip of Saudi Arabia not traversed by an outside traveler on foot since the days of Lawrence of Arabia, and not walked by Saudis at least since cars began bumping down old caravan trails in the early 1940s. And already, we are lost.

Jeddah’s suburban fringe is a maze, a scribble of plans, a palimpsest. The desert is sprinkled with fortress-like mansions. It is slashed by new fences, walls, power lines, roads that go nowhere. Thousands of mounds of dirt pimple the landscape: a spreading sea of landfill, evidence of a massive building boom. (All of Saudi Arabia is a construction site.) We are zigzagging toward a rendezvous with our two cargo camels. Tomorrow, they will be trucked to an empty crossroad. We must find them. But tonight we are tired. (Banounah has collapsed under his mosquito net.) I switch off my headlamp and close my eyes. I press my ear to the sand. I am listening for the hoof beats of wild ibexes, for swarming herds of gazelles, for the wind raking through a lush savanna. Instead, what I hear is Jeddah. The city emits a long, continuous, mechanical sigh into the night.

When the first humans wandered out of Africa, they stumbled into a paradise.

After fording the Bab-el-Mandeb strait that divides present-day Djibouti from Yemen, they encountered a green, green Arabia. No desert is eternal. Water once sparkled here: Rivers ran to the sea, chains of lakes glistened in the interior. There were marshes, flocks of birds, open woodlands. A thousand centuries ago, the notorious Empty Quarter of the Arabian Peninsula was a Serengeti.

A quiet golden age in Arabian archaeology is now unveiling that ancient world. Stone tools that look remarkably like those littering northeast Africa were discovered here recently. These finds have effectively doubled the record of Homo sapiens in the Arabian Peninsula, pushing it back at least 106,000 years. These data are reshaping the traditional “out of Africa” dispersal theory. Our great, primal journey across the globe—the ancestral trail that I am following—may be far older than we think. Moreover, one long accepted pathway of earliest migration out of Africa, north up the Nile Valley into the Sinai and beyond, is now being challenged bygenetic studies. DNA markers in living populations instead point due east: From Africa we spread first to Arabia, and then onward into southern Asia. The peopling of Europe appears to have originated from distant India, not the Middle East.

“Both routes could be correct,” says Abdullah Mohammed Alsharekh, an archaeologist at King Saud University in Riyadh. “The record of human expansion has big gaps. Humans went everywhere, chasing resources—water, animals to hunt, plants to eat. We didn’t walk in straight lines. We radiated. We scattered.”

At dawn Banounah lights a miniature stove. He boils two miniscule cups of tea.

Morning tea in the desert ‘burbs. The line in the sand is Banounah’s prayer circle. Photograph by Paul Salopek

We scatter north of Jeddah. We radiate along the tangents of roads, fences, piles of junk, searching for our two camels—for our new cameleer, a stoic Sudanese named Awad Omran. We scan the ruptured horizon.

“Craaaazy!” Banounah says in bewilderment.

Hours later, sopping with sweat, we give up. We call our camel support team. We summon Awad. We send our GPS coordinates: a business college marooned in the sand barrens. They drive to us. Our camels, Seema and Fares, stare skeptically down, with their enormous jet eyes, from the back of the truck. Like all camels, they expect the worst. The truck’s cargo winch fires up.

The world’s first walkers had no maps. I try to imagine this.

Our original journeys across the world featured no preplanned routes, no shortcuts, no destinations. The very concept of “destination” had yet to be invented. Each virgin horizon unfolded with an open-ended question: Where next? Having no preconceived places to go, the Stone Age pioneers were, by definition, never lost. We might be able to remember this feeling, but we cannot have it again.

Fares, our big bull camel, growls like a dinosaur when he is lowered to the sand in a sling.

Fares, airborne and grumpy, at the camel rendezvous. Photograph by Paul Salopek

Being lost, I think, must be a modern affliction. It requires a collapse of personal geography. And herein lies a paradox. As our species becomes more successful, more populous, we fracture the world into ever tighter panoramas—into countries, provinces, towns, neighborhoods, streets, houses, rooms, “private space.” In this way, a proportionally larger share of the planet becomes alien, exotic, threatening, unknown. Today, we take up residence in our navels. We forget: The entire world is ours. We possess it. It is ours to move through. The anxiety of becoming lost in it—the jail-yard lifer’s fear of losing sight of his cell—is another unhappy side effect, like bad teeth, of sedentary life.

A few Saudi friends have come to say goodbye north of Jeddah. They bring our last cool water for miles. We snap photos. We wave. We set off.

I consult my GPS. A reflex. I remind myself: The people who discovered the world were going nowhere.

Navigating Jeddah’s booming margins by GPS. Photograph by Paul Salopek