[BenOfTomorrow]

You can look at history as well. Australian aboriginal homo sapiens were isolated for 40,000-50,000 years or so without any speciation.

You'd need an isolation event and a VERY long period of time; we have much more control over our environment than the aboriginals, which would probably serve to minimize differences in selection pressures between isolated populations to a far greater degree. 50,000-80,000 years doesn't come close to long enough, IMO.