Yes, its is supposed that ancient africans-(bushmen,of the kalihari, it would seem from dna evidence) moved out of africa and populated the world.. but PIE seems to be much later!
this is based on certain words(like tree names, and animal names, and weather words) that suggest PIE or what ever you want to call the UR language was from a people who lived in a temperate (not tropical) climate.
bushmen have a very interesting language-- its the only surviving one with clicks (!) and whistle like noises.
interestingly, wild animals are spooked by human voices, but not by clicks or whistles (and many birds are not spooked by a bell round the neck of a cat!) there hasn't been enough time (or animals are not smart enough to recognize a pattern in a whistle/click noise but humans can and do! --so bushmen language is especially good in a hunter/gather environment.
its is speculated the the first languages made more use of these type noises. (aboriginal austrailians, surprizingly, are the closest genentic link to the bushmen... with almost no 'intervening' populations! because of changing water levels of the oceans, most of the 'path' of the first 'great migration' is now under water.
there was a 6 part PBS special about this (the genetic proof of migration, with just a comment or two along the way on languages!) last year, (there is a 'companion book')
exploring the migration of 'people (genetically with DNA markers) gives surprizing insite into 'language groups' too!
the centeral plains of asia extending into eastern europe seem to have been a great reservoir where population grew, and from there migrated to many other places, (south to india, where they displace the sparse population left over from the first great migration), west to europe (where they got isolated for a while) East to all of asia (in the meanwhile, older (first migration people) had moved into indoneasia, and were gettting ready to move to polyasia--
the last places 'explored' were the americas.. (and DNA/blood typing proves there were at least 2 major, seperate migrations. (languge groups support this too!)
