Mike, you asked:

"What kind of evolution does he mean?"

I mean the kind of genetic change in regional human populations that has always happened. From the expansion of Indo-European and Austonesian-speaking people about 5000 years ago, the Mongolian and Turkish-speakers 1000 years ago, European expansion in the last few hundred years, to East Asian and African people's expansion more recently. Your post way back as "Out of Asaia - Not Africa" hints the same process was involved in Homo erctus evolution and I have provided a link for the chimp/human split that shows the same process was involved then.

RicS wrote:

"The Great Wall of China had its uses for around a thousand years."

Yes. But it was never totally effective.