Today, nonhuman apes are few in number and face dire extinction risks in the face of human-driven impacts like poaching, habitat loss, and climate change. In the Miocene epoch, between 23 to 5.3 million years ago, the world was much less grim for apes. During the majority of time, the Miocene apes were diversifying, inhabiting new environments, and evolving new adaptations. There are only eight ape genera alive today, including our own genus Homo, but as many as 50 genera of fossil ape have been identified in Africa, Europe, and Asia during the Miocene. Given the rarity with which animals are preserved as fossils, these species surely represent a fraction of the true diversity of apes during this time period. It was a veritable planet of the apes!
In the early Miocene, Africa was an island continent where a diverse cohort of ape-like species coexisted in the forests and woodlands of what is now Kenya and Uganda. These early apes were likely the predecessors of the common ancestor of living apes but had evolved only a few of the defining features seen in living apes.
One of the best-known species, Ekembo, had a long and flexible back, narrow ribcage, and restricted joint mobility. These features suggest that this animal was an above-branch quadruped, moving through the trees by climbing cautiously on all fours on top of branches. Despite having a more monkey-like body plan, Ekembo’s lack of tail allows us to recognize it as an early ape. Another species from Kenya, Afropithecus, provides the earliest evidence that an ape-like life history, or pattern of slow growth and development, was present 17 million years ago. These early Miocene species show that the key features of living apes did not appear as a single unit, but evolved in a mosaic fashion, where individual traits appeared at different times within distinct lineages.