An inconvenient fossil
In 2007, a team of paleoanthropologists announced a discovery from the Chorora Formation in Ethiopia's Afar region: nine fossil teeth. The teeth belonged to a previously unknown extinct ape, which they named Chororapithecus abyssinicus. "Chorora" refers to the geological formation where they were found, and "abyssinicus" references Abyssinia, the former name of Ethiopia. The fossils—eight molars and one canine—were found at the Beticha locality and belonged to at least three different individuals.
Initial analysis showed the teeth were remarkably similar in size and shape to those of modern gorillas. The molars possessed the high shearing crests adapted for a diet of fibrous vegetation, like stems and leaves, which is characteristic of gorillas. Based on these features, the researchers proposed that Chororapithecus was an early member of the gorilla lineage (tribe Gorillini). The discovery was significant because, at the time, the fossil record for great apes in Africa between 12 and 8 million years ago was almost completely empty. This gap led some scientists to hypothesize that the ancestors of modern African apes had evolved in Eurasia—where many ape fossils from that period are found—and later migrated back to Africa. Chororapithecus provided direct fossil evidence of a great ape lineage living in Africa during this period.
Recalibrating the human story
The age of the Chororapithecus fossils became a point of scientific discussion. The initial dating placed them at 10 to 10.5 million years old. This age suggested that the last common ancestor between the gorilla lineage and the human-chimpanzee lineage must have lived even earlier, pushing back the timeline of hominid evolution by at least two million years compared to estimates from genetic studies.
Later analyses of the volcanic rock layers surrounding the fossils revised their age to approximately 8 million years old. This younger date aligns more closely with molecular clock estimates for the human-gorilla split. Even at 8 million years old, the existence of a specialized, gorilla-like ape in Africa contradicts the idea that African apes are descended from European ancestors like Dryopithecus. If Chororapithecus is indeed an early gorilla, it supports an African origin for all great apes. The discovery, along with the 10-million-year-old Kenyan ape Nakalipithecus, suggests a continuous presence and evolution of great apes within Africa. The debate is not settled, as the entire species is known only from nine teeth, but these fossils remain an important piece of evidence in the story of where our deepest ancestors came from.