MP makes the working assumption that whatever happened to allow FL to emerge in its current state happened recently in evo time. This, in turn relies on assuming that precursors of us were without our UG (though they may have had quite a bit of other stuff going on between the ears, in fact, they MUST have had quite a bit of stuff going on there). This assumption was recently challenged by Dediu and Levinson (D&L). Here's an evaluation of their paper by Berwick, Hauser and Tattersall (BHT) (here). BHT argue that there is no there there, a feature, it appears, of much of Levinson's current oeuvre (see here). They observe that the evidence for the quick time frame is sorta/kinda supported by the archeological record, but that such evidence can hardly be dispositive as it is not fine grained enough to address the properties of "the core linguistic competence" of our predecessors as this "does not fossilize." However, such that exists does appear to (weakly) support the envisaged timeframe proposed (roughly 100,000 years). Indeed, as BHT note, D&L misrepresent an important source (Somel et. al) which, concludes, contrary to D&L that: "There is accumulating evidence that human brain development was fundamentally reshaped through several genetic events within the short time space between the human-Neandertahl split and the emergence of modern humans."
So take a look. The D&L paper got a lot of play, but if BHT are right (that's where my money is) then it's pretty much a time sink with little to add to the discussion. You surprised? I'm not. But read away.