Primates are principally dwellers of the tropics and subtropics. There ain't so many monkeys and Apes in northern and far southern climes.

Also, although there are demonstrable "waves" of humans who pushed other groups to the fringes (e.g. Picts and Celts in Northern Europe, Cro-Magnon and Neanderthal man), nonetheless the genetic information tells us that EVERYONE that we would call human is related back to that small group in Africa principally by matrilinear descent.

Sure, originally there were probably "other" groups outside the territory of the "out of Africa" mob, but in time they were squeezed between the advance of this wave and the limit of their allowable habitat. They died out. THEN the Out-of-Africa mob spread even further, to new places where there had NEVER been humans of any kind before.