Image Source: TimVickers at English Wikipedia.
The fossil record of our ape ancestors in Africa is almost nonexistent for a period of about 8 or 9 million years. This long gap lasted from about 16.5 million to 7 to 9 million years ago, during the Miocene geological epoch.
Yet fossil remains in Europe and Asia show an abundance of ape species flourishing and evolving new traits during that gap period for African apes.
The unanswered question is: How did the current ape species found in Africa evolve?