You mean like Sundaland? I don't even bother discussing anymore.
For what it's worth the Chinese are finding that their core culture BEGAN in foothills above 2000 ft. elevation in Western China ~ much of it in Inner Mongolia.
What I've learned over the last few days is that 2000 ft elevation marks a major difference in rainfall in an area ~ above that height, you have recurring semi-arid climate. Smaller mammals as well as both odd and even toed ungulates live there in significant numbers.
Lower than that you find large predators and large prey animals, and deep forests. Unless those guys all die the smaller mammals cannot move into the estuaries of the great rivers in the region. About 10,000 years ago the hill cultures in the West moved down hill and East. About 5,000 years ago the Chinese plains were heavily settled but the guys with the higher technology still lived uphill to the West!
The Chinese really wanted it to be different but the radiocarbon dating shows the West to be more ancient than the East.