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 a

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.