they have identified 11 such "Y chromosome descent clusters," that is, groups of related men who may trace back to a single male ancestor. They estimate the date of the founder's life based on the number of random mutations that have crept in since. I thought it was interesting that they date the founder of the putative Genghis Khan lineage (DC1) to 1060 AD, which would make the founder Genghis Khan's great-grandfather.
These techniques are new and I still take the results with a grain of salt. But this stuff is getting better all the time, and within a decade or two we should have real maps of human migrations, approximately dated, across the entire globe.