As I understand it, all populations outside Africa have at least 2% Neanderthal ancestry. In eastern Asia and I think Papua New Guinea in particular that percentage could be more than 4%.
Now you also have the Denisovans from which a full genome sequence from a small bone fragment have been found in Denisova cave in central Asia. The latest research suggests that some Asian groups have about the same Neanderthal ancestry as other non-African populations but more Denisovan ancestry.
Question: If we theorize that East Asians (Chinese, Koreans, Japanese) with their characteristic features are not the result of recent evolution as per the "recent out of Africa Theory" but are instead the result of hybridization between modern humans and some form of archaic human (just like the Neanderthals and Denisovans) that have yet to be found.
To what degree could this theory be proven or disproven from genetic studies?