Welcome to EvC. There's lots to learn here.
To get this topic off to a good start(and I think it is a pretty good one) could you pick a better title?
How about something like "Human speciation due to geographic separation"?
There are real biolgists here who will be able to point you to the answer to this question.
If you change the title then I think this should be promoted. It might also be a good idea to suggest what boundaries you would like on the discussion. For example, can this talk about the example of other non-human groups or are you intending to restrict it a lot.