At some point, human ancestory can be traced to Africa. Australiopithecus and Homo Habilis for sure. I think various Homo Erectus evolving into the various races of Homo Sapiens is a compeling theory, I even believe it is more likely than not, but this discovery hardly disputes OOA. If any single group of humans wandered persuing game, than it is very likely that within only a few thousand years they may have well migrated 10,000 miles. Certainly at this time there were huge migration of fauna--horses and camels to the old world, bison and elephants to the new. Has anybody postulated how long it took for horses to appear in say, Spain, or Asia Minor, as opposed to Tibet or China?
I believe Victor Mair covers that in his book The Tarim Mummies.