Apricots are dried on a Hunza Valley rooftop. On the flanks of the magnificent Karakoram mountain range, a jagged spine of 25,000-foot-high mountain spires, lies the valley of the Hunza—a place so rich in beauty and long-lived people that it is credited as an inspiration for James Hilton’s novel of utopia, Lost Horizon. At over 8,000 feet in elevation and ­physically isolated from the rest of the world, it’s not a typical ­agricultural paradise, yet the rich ­volcanic soils and abundant water have made it one of Pakistan’s most productive agricultural regions and the ancestral home of a unique ­apricot. […]