Up until very recently, much of Africa(and other parts of the world) was unclaimed by any state.
Apart from a chunk of Antartica, however, that is no longer the case.
So, would their be a reasonable chance with any divergence within the last 250 years for their to remain extensive unclaimed(or at least unclaimed by serious states, Sealand-style claims don't count) territories in Africa? Could all those thoroughly disorganized tribes remain undisturbed?
Oh, and as an addendum- the technology science and economy cannot be significantly wore then it currently is- ie. the unclaimed and uncontrolled areas must not be that way due to backwardness of the world as a whole.