The percent difference between genomes of species is one of those tricky measures that doesn't really give good intuition. I find it much more useful to think in terms of the time since two species shared a common ancestor.
e.g. For humans and chimps, that's several million years. For Sumatran and Siberian tigers, it's around a hundred thousand years.
So not that far away since modern humans began splitting up into separate subgroups outside of Africa? Of course there have been quite a bit of intermixing since then (more so in Eurasia than the more isolated parts of the world before the modern times, though)
There are estimates that the most recent common ancestor of all humanity lived a few thousand years ago. Isolated peoples are almost never fully isolated, and all kinds of rare events can happen in 100+ generations. Andamanese peoples in particular were in contact with each other, with occasional contacts to the mainland.
Tasmania may have been isolated for ~8000 years between sea level rise and European contact. But the last person of fully Aboriginal Tasmanian descent likely died in 1905.
Out of africa remains defensible but more and more people will come to the conclusion that the chinese hyporhesis of the multiregional origin is somewhat true so we will get a hybrid i guess
The problem is that "Out of Africa" is an uninformative name. The outflow from Africa was well underway 100k years ago or even 200k years ago, and there was no inherent break between that ongoing outflow and what happened 40k years ago when (inasmuch as we can reconstruct today) behaviorally modern rather than 'archaic' humans began to migrate out, which we now call "Out of Africa". So it's hard to even tell apart the "recent Out of Africa" and the "multiregional" hypotheses in a way that might help settle a debate.
