Mea Culpa for falling behind.

Bostrom mentions ( p55 ) that the increase in human population and organizational complexity since the Pleistocene suggests that we have created "superintelligence relative to a Pleistocene baseline". And we have radically changed the world, in an accelerating fashion, from that baseline. Yet it seems plausible that Pleistocene tribes could have "slipped through the cracks", perhaps in the Amazon or Pappa New Guinea, and continued living much the same style of existance since then. Since this seems less plausible for what we conventionally refer to as superintelligence, this suggests there is some sort of dis-analogy that is being overlooked here.