What struck me was a side rumination of Razib's:
And is it plausible that human artefactual technologies could persist for tens of thousands of years? Some perspective: 15,000 years before the present would take us back to the last Ice Age, past Rome, past Sumer, past the Neolithic. But what about the Olduwan and Achuelean tool traditions, they persisted for hundreds of thousands, even millions of years across the span of the World Island (Eurasia + Africa)....This is interesting stuff. Though goodness knows there are enough ideas as to what it means to "be human" one of the persistant definitions is "man is a rational animal". Rolled into the use of that word "rational" is a host of other statements that set us apart from the creatures with which we share much of our DNA: "man is an imaginative animal", "man is a problem solving animal", "man is a spriritual animal".
What does this have to do with the paper in question? If the exact same cultural tradition persisted for tens of thousands of years (a range given in the paper would be 75 K BP to 35 K BP) that is strong evidence to me that the perpetuators of that cultural tradition were not yet "human" in a the way we understand human, for humanity is protean, changeable, fickle and restless with creativity. On the other hand, it could be the relationship between the East African artefacts and the Indian ones is coincidence which happens to span tens of thousands of years, just as ancient eastern North American cultural traditions seem to bear some resemblance to the Solutrean tradition in Europe which predates it by 10,000 years. Myself, I lean toward the former, that is, that "modern" cognition, which allows for the explosive and unpredictable tacking of cultural traditions is a more recent innovation than we might have thought.
So when we talk about the origins of the human species, the really inriguing question is, when did our ancestors start doing all these things? When did art first appear? When did man begin to consciously shape his environment by using technology? When did man begin to wonder where he came from?
None of this is readily apparent from fossil, genetic or archeological (except perhaps the art question, though there the question of what art is becomes rather tricky) evidence. But as Razib points out, there may have been some period in which rather human-looking creatures wandered the earth wielding stone tools, yet making those tools more as a matter of instinct than invention.
What does seem significant is that nowhere on earth (although some populations remained isolated from the rest of the world for dozens of millenia in places like Australia) do we find humans (or human-like creatures) who are not capable of cognition, art, invention and spiritual/philosophical curiosity. This seems to me to suggest one of three things:
1) The change that produced these characteristics took place quite a while ago, clearly before the most recent common ancestor of all living humans.
2) The change was in some sense innevitable, so that all human populations developed these characteristics despite living in separate places with separate population and environmental pressures.
3) The change is in some sense fundamentally not physical, and is not strictly at matter of DNA.