Mongolia is the ultimate point of origin for 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 and pressing on their neighbors. (Chinese historians refer to the constant incursions of "Hsiong-nu" from the north.) As a result, Mongolia is a net donor of genes. 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, Central Asia, Russia, the Ukraine, and even pieces of Central Europe. This has happened four times:
Ironically, if your ancestors are from Mongolia, none of this really matters, since it was a net donor of people to other regions. There are some exceptions, however:
The thirteenth century: In the cosmopolitan Mongol Empire, people moved relatively freely. The Mongols especially imported skilled craftsmen and slaves from all over their empire. Indeed, they employed talented people whereever they found them. This was not limited to Marco Polo. During the height of their empire, French sculptors, German miners, and many others worked in the heart of Mongolia. Iran and Central Asia were particularly favored sources of skilled labor. If your ancestors were in Mongolia in 1490, they could easily have had ancestors in any of the Mongol Empire in CE 1000, but Iran and Central Asia are particularly likely.
The eighteenth century: The Manchus take over Mongolia and China, establishing the Qing Dynasty. The administrative backbone of this empire were the ethnic Chinese. If your ancestors were in Mongolia in 1800, they could easily have had ancestors in Manchuria or China proper in CE 1490.
1911: Mongolia becomes independent with the collapse of the Manchu (Qing) Dynasty. From 1918 to 1925 it was a wrestling mat for Bolshevik, White Russian, and Chinese forces. Following its conversion to a Communist state in 1925, the only foreigners present in force were Russians. If you are Mongolian, your family folklore will tell you if there are any Russians or Chinese in your recent background.