Awesome map at http://www.bradshawfoundation.com/journey/
Thanks for the link.
However, one thing the map makes clear is that the spread from Sundaland occurred well before the submersion of Sundaland as the climate moderated during several periods prior to the last glacial maximum.
My guess would be that the Caucasians came largely from the Middle East and maybe the Indus Valley and that the Mongoloids came from Southeast and East Asia.
However, both Northern Europeans of the German, Slavic and Fenno-Ugric linguistic groups, as well as the Han Chinese, Koreans, and Japanese are very cold-adapted. Their ancestors may have been trapped in refugia farther north in Eastern Europe/Central Asia or in the northern parts of East Asia.
Having been severely selected by climate, they then expanded out of these areas and became relatively successful emmigrants.
This is the same map explained in Oppenheimer's book, Out Of Eden, but is not contained in that book. His previous book, Eden In The East, portrays a little different story.