Gorilla or not, several experts agree that an ape of this antiquity in Africa strikes a blow at a hypothesis that the common ancestor of African apes arose in Eurasia and migrated to Africa. "These are very important fossils," says Alan Walker, a paleoanthropologist at Pennsylvania State University in State College. "They show that apes have always been in Africa--that they didn't come from Europe and Asia."
Paleoanthropologists have known for decades that apes (Hominoidea) arose in Africa, where researchers have found diverse apes from 22 million to 12 million years ago. But despite many searches, almost no ape fossils have been found in Africa between 12 million and 7 million years ago, with the notable exception of a 9.5-million-year-old upper jaw from Kenya. Some researchers inferred that apes went extinct in Africa while other apes flourishing in Eurasia gave rise to the ancestors of modern African apes.
This is an important issue. I was reading a book chapter the other day that concluded that the origin of nearly every higher-level primate group may have involved rafting; in that account catarrhines originated by rafting from Eurasia to Africa, dryopithecines from Africa to Eurasia, and possibly the African ape-hominid clade by rafting or walking back to Africa. These peregrinations been a feature of hominoid evolutionary hypotheses for the last 15 years or more. Possibly it is all an illusion -- only reflecting the rarity of Late Miocene fossil apes from Africa and their abundance in Europe.
Still, the dryopithecines really do look like plausible ancestors for later apes in many ways. More on that later.
Gibbons A. 2007. Fossil teeth from Ethiopia support early, African origin for apes. Science 317:1016-1017. doi:10.1126/science.317.5841.1016a