:Read the cited materials completely, on how the term "Southeast Asia" is used.  Hammer's quoted definition of "Southeast Asia" INCLUDES "Southern China" as well as "Southeast Asia" proper, as I stated above.  Rice farming originated in "Southern China", and then were introduced into Korea from China.  Bronze, and iron were also introduced into Korea from China.  So if the DNA shows that such a migration took place, it's natural to assume that the technology transfer followed the same route.