Nice work. Your mentioning of Har1 got me sidetracked looking into all we know about various accelerated regions. Real cool stuff, but all work in this field is still in progress. Its fascinating that the har1 region is identical in almost all humans, but so different in other apes. I wonder if it was a single event that changed all those basepairs or some nearby genetic factor that temporarily made it a hot zone for mutations. Possibly a duplication allowing one copy to vary widely...who knows.
My first thought was a dietary change that 'fed' the region something it was until then starved of. I've no reason or evidence for that, just an idea, as we learnt to produce fire and communicate in slightly more elaborate ways. The timing isn't so far off. Then again it could literally just be a random mutation never experienced before, who knows!