Recent discoveries again suggest any theory of exclusive development of hominids in Africa might not be tenable as Ancient fossil teeth, said to be 9.7 MIllion years old, thought to be from an ape like (hominid) creature have been found in Germany.
http://www.independent.co.uk/news/science/teeth-fossil-human-history-evolution-development-germany-rhine-mainz-archaeology-a8010506.html
This is several million years older than jaw and teeth remains found in Greece and Bulgaria.
Whether these particular creatures, or for that matter many other hominid creatures, were or were not ancestors of humans is open to question since the science suggests that there were many hominid species, most of which were "dead ends".