Vast stretches of Central Asia feel eerily uninhabited. Fly at 30,000 feet over... Turkmenistan, Uzbekistan, Kazakhstan -- and there are long moments when no town or road or field is visible from your window. Wandering bands and tribes roamed this immense area for 5,000 years, herding goat, sheep, cattle, and horses across immense steppes, through narrow valleys, and over high snowy passes. They left occasional tombs that survived the ages, and on rare occasions settled down and built towns or even cities. But for the most part, these peoples left behind few physical traces of their origins, beliefs, or ways...