Graeme M said:
I think it's intriguing that you suggest an evolutionary bifurcation that happened abruptly. Do you think capacity for language arose simultaneously or that the initial changes led to that capacity emerging?
One of the reasons I keep responding to this thread is that I think you are asking the right questions, Graeme. This tells me that you are thinking about the subject in an informed fashion. As far as your question I quoted above, I'd say, yes, what happened was that the gross increase in the size of the hominin frontal cortex reversed the direction of information flow in the hominin brain and
then language, math, musical ability, logical thought, all of that fell out from that bifurcative reversal. It's a story of how brain regions confer dominance over others as far as their neurodynamics. The specifics are complicated but the general idea is very simple and straightforward. Of course, for the record, this is my personal model.
Graeme M said:
Do you broadly agree with McNeil's work around the close association between gesture and spoken language?
I'm too lazy to review that paper right now as I have been up for the past 24 hours crafting this paper for the deadline of the IJCNN-2017. If the paper gets accepted (which it will because I'm co-writing it with one of the conferences main organizers

), then I will be spending a week in Anchorage, Alaska in May. Woopie..
http://www.ijcnn.org/
I was really excited about visiting Alaska until I remembered Tony Montana's take on it...
I'll be sure to dress warm!
As far as your comment about the common substrate coming out of the motor cortex regions associated with Broca's area, the answer is yes, this is the general idea. There have been many speculations of this nature over the decades, and again, If I weren't so tired, I'd offer up some references. The problem with all of these models, at least the ones that I have read, however, is that none f them posit, again, a major bifurcative event as triggering the
complex of uniquely human traits. This is where they missed it. I call this a kind of "reverse Darwinism." Right? For hundreds of years people held to the OBVIOUS view that there is something qualitatively unique about the mental capacities of the human species, but the whole thing got confounded because of the notion that there was a "god" that put a soul in humans. Then Darwin came along and said we're nothing but an average ape (DON"T make a monkey out of me!). Oh yeah, that sounds good. Sounds scientific. Now we can dump the whole god thing and be scientific about it. So, for the past 100 years everyone has been striving to demonstrate that we are just like every other monkey and that every other monkey is just like us. Right? This is the reaction against the human soul argument. But I think they overshot their mark and for the past 15 years I have argued with these people at academic conferences and still argue with them.