We'll Get to the bottom of this using DNA
Nuclear and Mitochondrial Analysis of ancient Mongolian sample
"A majority (89%) of the Xiongnu sequences can be classified as belonging to an Asian haplogroup (A, B4b, C, D4, D5 or D5a, or F1b), and nearly 11% belong to European haplogroups (U2, U5a1a, and J1). This finding indicates that the contacts between European and Asian populations were anterior to the Xiongnu culture, and it confirms results reported for two samples from an early 3rd century B.C. Scytho-Siberian population (Clisson et al. 2002)."
Read this:
On The Presence Of Non-Chinese At Anyang
Pretty Blond Headed Mongoloid Girl
Wouldn't be unrealistic to find various Steppe peoples as genetic ancestors to all the various types of Chinese though. The Silk Road did run through the place and there was always a strong trade in women.
However, I was referring to the "historic" Huns, a specific band of which left China and arrived in Europe ~ some sources say it took as little as 130 years, and others say it took 200 years for that trip.