Bear in mind, you don't need regular trade routes from Andes to Tibet, you only need the tiniest "leakage" (e.g., one outcast per 250 years leaving/entering the

Bear in mind, you don't need regular trade routes from Andes to Tibet, you only need the tiniest "leakage" (e.g., one outcast per 250 years leaving/entering the Andes, one outcast per 250 years leaving/entering Tibet, one explorer per 25 years starting after 1400AD traversing the Atlantic, that would probably be more than enough). In their paper, Rohde et al take all this into account, they do their homework, see p. 564 for the data they use about most recent establishment of routes. I'll quote this interesting tidbit from the paper: "Several factors could cause the time to the true MRCA or IA point to depart from the predictions of our model. If a group of humans were completely isolated, then no mixing could occur between that group and others, and the MRCA would have to have lived before the start of the isolation. A more recent MRCA would not arise until the groups were once again well integrated. In the case of Tasmania, which may have been completely isolated from mainland Australia between the flooding of the Bass Strait, 9,000–12,000 years ago, and the European colonization of the island, starting in 1803 (ref. 13), the IA date for all living humans must fall before the start of isolation. However, the MRCA date would be unaffected, because today there are no remaining native Tasmanians without some European or mainland Australian ancestry." To force the IA older than 9000-12000 years ago would require Tasmania be totally isolated, without even a single sexually productive immigrant/emigrant per 1000 years, for all that time. http://www.stat.yale.edu/~jtc5/papers/CommonAncestors/NatureCommonAncestors-Article.pdf http://www.stat.yale.edu/~jtc5/papers/CommonAncestors/Nature...