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According to what's known as the "Steppe Hypothesis," a group of horse-riding pastoralists living on the steppe around the Black and Caspian Seas migrated west into Europe and east into Central and South Asia around 3,000 B.C., bringing knowledge of horse breeding and the forerunner of Indo-European languages with them. A new genetic study, however, is now throwing cold water on parts of this long-held theory.

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• What is The Eurasian Steppe?
• The Eurasian Steppe, also called the Great Steppe or the steppes, is the vast steppe ecoregion of Eurasia in the temperate grasslands, savannas, and shrublands biome. It stretches from Romania and Moldova through Ukraine, Russia, Kazakhstan, Xinjiang, and Mongolia to Manchuria, with one major exclave, the Pannonian steppe or Puszta, located mostly in Hungary.

• What is the Dzungarian Narrowing?
• On the east side of the former Sino-Soviet border mountains extend north almost to the forest zone with only limited grassland in Dzungaria. 

• Where is Dzungaria?
• It's the north bit of northwest China, adjacent to the Tarim Basin.

• Anything interesting ever happen in the Tarim Basin?
• Well, the Silk Road ran along the northern and southern edges at various times, the western terminus of this portion of route is at Kashgar.