STARCHY, CIVILIZED ETHIOPIA rolls to a stop at Arba Minch, delivering your first triumph over the enigmatic national tongue known as Amharic: welcome to Forty Springs. Lush with palm-frond flora and breezy sapien fauna, Arba Minch affects a relaxed, anything-goes vibe, a tropical tonic for life in the uptight, pious north.

Ethiopia’s youth hordes tumble into a final pileup here, proof that Africa’s most populous nation after Nigeria, 2,000 miles to the west, exudes a passion to propagate. Almost half of Ethiopians are younger than 18 years, about 50 million youth in all. Like pilgrims parting a sanctified darkness, students from the university stream down into Arba Minch at night, illuminated only by their glowing phone screens. As they crowd the cratered roads, vehicles bearing outsiders bounce past, climbing to a high point.

Sunrise brings forth shimmering revelation. While the forty minch remain concealed and thus somehow mythical for the casual visitor, liquid smooth and sloshing glistens the daytime scene. From the terrace of the Paradise Lodge perched on an escarpment at one end of town unfolds one of East Africa’s most sublime panoramas. Two mighty Rift Valley lakes come together, separated by a narrow hump of land known as the Bridge of God. To the left one admires the milk chocolate expanse of Lake Abaya, while a pivot to the right brings smaller, darker Lake Chamo into view.

Dimly perceived, about six miles across Chamo’s waters, festooned with ravenous Nile crocodiles more than 12 feet long, sits lonely Nechisar National Park, named after the white grass of its desiccated plain. Thousands of zebras roam there today, a remnant of the varied beasts driven or hunted out in past decades of political upheaval. Like cousins of Madagascar’s skittish stars, the wild residents of Nechisar fled into exile with predators at their backs – in this case marauding Marxists.

A visitor to Paradise relaxing on the lofty terrace one day in August – a rainy, cool month in the highlands of Ethiopia – would have paused with his glass of trembling beer suspended in the fading afternoon light as an odd spectacle hummed into view.

A craft smaller and quieter than an Ethiopian Airlines turboprop, workhorse of the domestic aviation fleet, had risen from Arba Minch’s diminutive airfield, soaring past Paradise, climbing above the Bridge of God and a dense, darkening forest below. A winged, windowless tube accompanied by a distinct 3 whirring sound. In a few moments, the mysterious machine banked sharply to the left, heading east for the battlefields of Somalia.

Leaving Arba Minch is the beginning of leaving Ethiopia. Yes, the political map still places you firmly within the sovereign bounds of the federal democratic republic, latest incarnation of a stubborn and secretive 3,000-year-old nation once ruled by divine, and sometimes divinely maddened, kings and princes. Chilled beer and warm injera, Ethiopia’s spongy, slightly sour mealtime staple concocted from the grain teff, will still be found down the road. Donkeys will reliably meander into your path and cattle may clog the roadway. Yet settled, highland Ethiopia waves farewell from Forty Springs, as the road snakes down the escarpment and makes its way toward the Konso lands to the southwest and eventually into the great and enveloping valley of the Omo River, where time itself drifts away.

The word Omo occupies a magic space in the mind of the highlander Ethiopian, for few have visited that far-off land. They will know pictures of women in braided, ocher hair, oiled breasts dangling, or lips stretched to grotesque lengths, or men resembling birds with hair feathered and fancied with red-mud plaster.

These mesmerizing images illustrate tourist ads, promotional videos, and storefronts in the city like come-ons for half-beast, half-human grotesques at a county fair in America. In this spectacle live people of supposed primitive mindsets, close to the mud, devoted to their cattle and guns, enthralled by strange, earthy rituals. Habits like requiring teenage boys to scamper naked over the backs of bulls to prove their manhood. The Valley of the Lower Omo is the other world that modern-feeling Ethiopians file away, possibly while scratching their heads, as they go back to Orthodox Christian and Muslim observances and five-year economic plans and social-media updates. Who are these people that time abandoned and what are we to do with them?

An American boy of the polyester 1970s, living in an era before the world was knit in a tangle of voices and a torrent of instant images, would have asked the same. Opening a National Geographic or an anthropology textbook to ogle fantastic humans like these was glossy proof of an exotic world untouchable and perhaps unreachable even in the era of moon shots. Earth indeed was a planet of many worlds. And this world and its people were decidedly naked.

The highlander Ethiopian, on the other hand, is rather devoted to her garments. The land rises above 8,000 feet and brisk winds blow through the valleys. This is Africa’s Switzerland minus crisp ski runs and precision chocolate, an enthralling highaltitude land: the roof and water tower of Africa. In rainy season all is consumed by mist and fecund-damp growth.

Tanzania lays claim to Africa’s highest point, Mount Kilimanjaro, yet that cherished summit is a chubby, 19,341-foot-high oddball dormant volcano bursting from an elephant-studded plain. Ethiopia for the most part is majestic upthrust. Waves of rock roll from Arba Minch and its environs to the border with Eritrea hundreds of miles away in the far north of mesas and redrock vistas. Up there you expect to spy a cowboy charging across the frame kicking up a dust plume of horsepower.

From northern Ethiopian vistas the lofty land tumbles down to the eastern desert out of which lava gurgles and spits from otherworldly Technicolor pools less than 100 miles from the Red Sea.

In those remote, high mountains men may wrap themselves against the chill in a thick, nubby cotton cloak known as a gabi. Women will wear skirts of dark green, a uniform of the devout Amhara peasant, and may bear crosses tattooed on their foreheads. In the growing towns and cities of the central plateau, by contrast, T-shirts and jeans sheathe the urbanite. Slim young women, aware of their allure, gravitate toward tight skirts and slinky jackets according to the vibe. Skin may be revealed inside a dance club, yet on the street modesty prevails.

Yet let us spin our compass southward once more, for our journey leads that fateful way. Less than two hours out of Arba Minch, you stop for coffee in Konso, a town set amid terraced hillsides, and perhaps buy a Konso TV (delightful hand-drawn paper channels that unspool as you turn tiny bamboo rollers; the Obamas feature in one). Even here the unexpected may ruffle the calm.

Near Konso once, during a return journey from the Omo Valley, a deranged local hurled a rock at our moving vehicle with the force and velocity of a baseball pitcher, spidering the windshield with a terrific gunshot-sounding impact. A split-second difference and the projectile would have brained the driver through his open window. Yet fate was entirely on his side; the driver had commanded a battle tank in the border war with eccentric Eritrea and thus reacted with cool decisiveness. In 20 seconds, he halted the vehicle, leapt out into a crowd, collared the sullen culprit, and shoved him into the back seat for delivery to the Konso police station.

After Konso the road rolls toward a dramatic valley backed by a mountain wall. One’s mind expands along with the vistas, which begin to stretch for long miles toward hazy horizons. The air grows warmer as you descend. As you round bends in the road, children appear, dancing or holding aloft wooden AK-47s for sale. Along the route, clothing begins to fall away.

Young men stand along the roadside without shirts, and soon too their pants shrink, revealing weathered legs though nothing pendulous – yet. While the youth may toss a checkered cape over his shoulder as he displays a few trinkets, the fabric is an afterthought. Young women hint at going topless, with T-shirts straining. It will get a bit steamy out here today. While lips, hair and body art will attract their blinking shutters, the long lenses of the tourists are coming for the bare facts. Make no mistake. The clothesline descent toward the Omo Valley intoxicates with Stone Age titillation. There are rumors of European tourists secreted in Indigenous villages, throbbing with wild dancing, dazzled by the jeweled dome of night.

Before the highlander Ethiopians fully appreciated the untamed potential of the surging Omo waters, the tourists had alighted upon the passions of the pastoralists. With cameras and fat wallets they were turning the valley into a human zoological park. Bagging lenses as the sun dips, they roar off in Land Cruisers to drinks and dinner. You will run across these tourists en route to the valley at a charming lodge in the heights of Konso with a broad view from its stone-floor overlook toward the distant, sparkling watershed of the Segen River. The Segen is a mere stream when compared with the mighty Omo, yet valuable to parched herders wandering the precious grasslands out near Kenya’s most remote terrain.

At dinnertime, American, British, and German tourists mingle with aid workers and visiting doctors and nurses volunteering time. The Omo trail is rarely crowded and retains a flavor of exclusivity as if a portal is beckoning into an African Shangri-la. While small, organized tours haul most of these visitors into the valley, independent travelers do venture in. A couple from Los Angeles lingered one morning over breakfast, explaining their plan to wander into one of the last strongholds of deep-time Africa. A territory patrolled by muscular warriors cradling AK-47s and shadowed by suspicions.

Pastoralist ancients still afoot in these parts seem to regard the land as boundless, or as boundless as their prehistoric needs dictate. Their world of human interaction is bounded, at the service of elemental and recurring facets of life in a natural state. The 21st century Ethiopian nation-state presents a contrasting template: marking off the land into its political and economic uses and unbounding life’s consumer possibilities flowing from these utilities. A fracturing of ancient cultures in the march of earth movers, a growl of modernity that the state’s men insist heralds rescue from backward ways. “Competing paradigms,” we called it in our report from my first foray into the valley.

“The various tribes of South Omo have distinct and ancient cultures, usually based on an agro-pastoralist and mobile lifestyle,” said we envoys of Ethiopia’s major international development funders, governments American and European. “The Government of Ethiopia’s development plans for the region are based upon sedenterized and irrigated agriculture which it believes will greatly alleviate recurrent food security problems; a new departure for cultures whose livelihoods have remained unchanged for centuries.”

Or thousands or tens of thousands of years, who knew? Troves of hominid fossils and some of the earliest tools crafted by human ancestors have come to light in the Omo around 4-million-year-old Lake Turkana, which juts into southern Ethiopia though resides mostly in Kenya.

These tools are “evidence of the oldest known technical activities of prehistoric beings,” the United Nations explains in justifying designation of the Lower Valley of the Omo as World Heritage terrain. The discoveries, opines the world body, render these lands “one of the most significant for mankind.”

Hominid feet have pressed into this soil for what by our mortal timespans is eternity, perhaps a billion days. Time so elongated into the slanting equatorial sun as to transport us onto another planet altogether, the future so remote from those early bipeds that their present jogs in place, refusing to budge. We must whoosh forward like star voyagers into our time, our Earth, to arrive at the political map drawn by the latest evolution of human society on this much trod terrain: the Ethiopian revolutionary democrat. As a revolutionary, he’s rather reluctant; as a democrat, he’s a flawless fabricator.

Landlocked Ethiopia is divided into 10 regional states, some the size of countries (Amhara, the Ethiopian homeland in the north, is bigger than Bangladesh), and two city-states, the modern capital Addis Ababa, meaning New Flower, and the old French railway terminus in the east, Dire Dawa, pronounced “Dray-dawah” by highlander Ethiopians. Each state is split into zones that comprise districts known as woredas. The woreda is the basic administrative building block of the country, equivalent to a county in the United States. This political map roughly matches the ethno-anthropological one – so a woreda may capture the core lands of an Indigenous community such as the Dassanech along the Ethiopia-Kenya border near Lake Turkana.

Ethiopia’s highlander-dominated government rules the Omo lands – or more accurately, attempts to rule them - through district administrations parceled out among the native inhabitants. Ethnic federalism they call it, a creation of the Ethiopian People’s Revolutionary Democratic Front. And many of the administrators are drawn from the modernizing local ancients. They have made the transition, draped their skin in modernity, and grasped fragments of fabric and consumer civilization.

In the lower Omo, land and landscape overmatch people. In the central and northern regions of Ethiopia, villages abut villages, and these turn into ramshackle towns stuffed with jumbled little shops and dark, shabby cafes, maybe a hotel with lousy plumbing. These are pockets of hope. Poverty tumbles among people in proximity to an urbanizing area, according to economists at the World Bank who study patterns of migration and economic promise.

Impoverished Ethiopia often means isolated Ethiopia – distant from roads, stores, knowledge, health care and all modern conveniences, lacking car or bus, squeezing a living from the tired and often thirsty land though with few prospects for rising above subsistence. The farther one gets from Arba Minch, the 11 more one sinks into a sublime though perilous emptiness.

We move out from Konso territory. To reach Jinka, outpost of highlander Ethiopian power as capital of South Omo Zone, one must first descend into a basin that cradles the Weyto River. The approach reveals yet another glorious scene – a lovely green patch at the base of an imposing mountain wall. The green is elusive like a mirage and dazzling from a high, distant viewpoint.

Only when your vehicle descends to the floor of the valley do you realize that this is a farm, of cotton, stretching away to the south. This cultivation is the first sign that waters of this sculpted terrain might carry some mystical property, might infect men with grandiose desires, might shake the landscape from Paleozoic slumber. And we haven’t come yet to the majestic Omo River itself.

One of the mind-rending revelations encountered in Ethiopia is the utter mismatch between the musty impression of the place as a bone-dry purgatory for starving peasants, a tumbleweed graveyard, and the teeming water resources apparent in almost all corners of the republic apart from the arid Somali east.

The so-called Blue Nile begins its journey from Lake Tana in the northern state of Amhara and after a long, arduous trek nourishes Egypt. Not so fast, the Ethiopian planners say. With an Italian contractor moving the dirt and pouring the concrete, the Ethiopian revolutionary democrats have built a mile-wide plug 10 miles from the Sudan border in a design resembling a stepped Mayan pyramid.

The Grand Ethiopian Renaissance Dam, costing five billion dollars, harnesses this branch of the Nile before it escapes to Cairo, and generates electricity for sale to neighbors. Ethiopians rallied to their monolith with messianic fervor, investing their wages in bonds issued by the government to pay for this epic expression of revolutionary development greatness. The rulers in Cairo grow troubled in an existential way, in the manner of inheritors of a sun-drenched great civilization, as the Ethiopian tap settles into place.

The reservoir behind this river wall spreads to three-quarters of the size of Lake Tana, itself as big as America’s Rhode Island state, creating a major water feature on the map of Ethiopia for the first time in eons. More surprises await. West of Lake Tana, the road drops below an escarpment so lush it resembles cliffs in Hawaii, opening onto a bucolic landscape of crystalline streams and lovely forests. This is Benishangul-Gumuz state, which embraces the natural flow of the Nile up to the mega-plug.

The simple Gumuz people, more Sudanese than Ethiopian, balance loads on shoulder yokes as they stroll past stunning fairways, dogleg par-5s and rolling par-4s, a golfing paradise. If only there were golf, golfers, golf balls, architects, and tamed earth. One day the Ethiopians will discover how many Europeans they can lure across the Mediterranean with a cleverly positioned golf green and a beer cart steered by a local beauty.

Water replenishes savvy farmers too. Rains that fall hundreds of miles away on south-central Ethiopian fields yield a bumper crop of corn and wheat, enough that those farmers can sell their surplus to the humanitarian relief agencies for hungry mouths elsewhere. Where the land falls off from the highlands toward the east and bolts for the Indian Ocean the earth is indeed dry and sparsely populated, poor and austere. Only one in 16 Ethiopians perseveres there.

For months of every year the vital core of Ethiopia is wet, more Seattle than Sahara. As a friend steeped in the soil reminds me, more precipitation falls on the red-rock terrain of northern Ethiopia in a year than soaks London. The precipitation simply comes in torrents than in steady offerings, and slithers away before humans can detain it.

The Omo River, as we shall see, is perhaps most prized of all as gravity herds its waters down through cascades of southwestern Ethiopia and on to Lake Turkana. Three dams interrupt the descent. In its last stretch before emptying into Turkana, the Omo tours a landscape warm and wide, fertile ground the local ancients used to farm in modest plots as the flooded river receded. Outsiders notice that the black cotton soil clings to boots. They also take note of what this Omo-bathed land loves today: sugarcane.

Muscle and stubbornness that only the 21st century could muster would change the course of the river and its people. The Valley of the Lower Omo would become an agricultural stage worthy of imperial ambitions in an age without divine kings. In lands where human ancestors may first have chiseled implements to tame their surroundings and improve their harsh odds of survival, a new epoch of land, water, and sugar was taking hold. Yet the existential contest was still very much in play.