The region stretching from Central Asia through Mongolia to Manchuria is the home to some truly remarkable nations. Traditionally, people here have been highly mobile tribes of pastoral nomads. When not tending their herds, they would practice the arts of war, raiding one another. If your ancestors lived in any part of this broad region in CE 1000, their ancestors were probably spread all across it in CE 1.
At certain times, they have become united and directed their energies outward, migrating into and ruling surrounding nations, including China, Afghanistan, Northern India, Iran, Russia, the Ukraine, and even pieces of Central Europe. This has happened four times:
Ironically, if your ancestors are from Manchuria, none of this really matters, since was a net donor of people to other regions. There are some exceptions, however:
The thirteenth century: In the cosmopolitan Mongol Empire. The Mongol rulers developed an excellent communication system and employed talented people from all over their domains, so If your ancestors were in Manchuria in 1490, they could easily have had ancestors in any of the Mongol Empire in CE 1000.
The seventeenth century: Three hundred years after the breakup of the Mongol Empire, the Manchus, in a major role reversal, take over Mongolia and China, founding the Qing Dynasty. Ironically this was the beginning of the end for the Manchu nation, as they were spread very thin governing a large empire and were genetically swamped by the ethnic Chinese whom they governed. At this time, the Manchu language is spoken only by a handful of elderly people. Thus, if your ancestors were in Manchuria in 1900 or 1800, most of their ancestors probably came from China proper in earlier periods.