There is a very credible theory that the Asians are more likely to have come from Java than Africa.
Those Mongol genes spread themselves all the way to Syria and Hungary. I was reading an article that said 1 in 6 Hungarians still to this day have oriental genes in their DNA.
If you go far enough back Korea was a part of the Qing dynasty. Until the 1950s they were still using Chinese characters to write with and government documents were kept in Chinese. They have a distinct advantage in studying the language. That, and with the amount of Korean schools in China were lessons are taught in Chinese, they have that as part of their modern learning.
If you go far enough back you'll find that Chinese, Koreans and Japanese are all from the same stock. You'd have to start re classifying gene pools to prove otherwise, just as the French and English, they're from the same stock.
If they wanted to go even further they could probably even say red Indians are in some form Chinese, as they can be trased back to the Heilong River tribes in Northern China.
China is a big place with 56 minorities, it has its fingers in a lot of pies. The Karen in Burma, homeland in Ruili. The Dai from Xixuangbana had an empire that stemmed through Laos and Thailand. The Wa in LinCang have almost annexed WaBang as China and they have their roots as far as the Thai border and Northern Burma.
The Japanese are also from Chinese stock, or an area of which is now China. They based their society on Chinese culture and use a lot of Chinese characters in their written language.
The original natives of Taiwan are the Gaoshan tribes. These people have Chinese as well as Polyneisian roots. Everyone else in Taiwan can probably trace their a destroy back to Xiamen or Zhejiang in some way.
There is historical evidence that could prove any of the claims outlined, some concrete, some would have to rely on sheds. But fact is the area which is now China has a big genetic pull on most of the surrounding countries. Those borders weren't there 200/300/500 years ago.
It would just be arrogance to dismiss your students if that was ever brought up. Chances are the student wouldn't know their arse from their elbow if they had to explain any further than tht statement itself, however the statement could stand on its own.
If the student wanted to get really adventurous they could even say that Chinese DNA were in one or two of the Yemeni Hill tribes, and there would be evidence to prove that.
Hate to rain on everyone's Chinese don't know what they are on about parade here, but in this instance if you got your head in a history or genetics book, these things would pop up in more detail.