Ever since Charles Darwin, the idea that humans originated in Africa from an ape ancestor was hotly debated, but progressively gained support. The British naturalist, however, was unable to determine the kinship between humans and modern hominoid primates (gorillas, chimpanzees, orangutans, and gibbons). Recent molecular studies, however, have determined that humans and chimps share a common ancestor (LCA) that lived during the Upper Miocene, between 9 and 7 million years ago, a fact that is frequently interpreted as evidence that it was chimp-like. This idea has dominated discussions of human ancestry for decades, and consequently, the more primitive Miocene apes were excluded as potential candidates. There are two major points of view in assessing the role of the ape fossil record in our evolutionary history. One rejects the idea that they are relevant in the debate over the origins of humans, while others think they play a crucial role. The fact that today’s hominoids are just the survivors of terminal specialized branches of a group that was much larger and more diverse in the past, provides little evidence for the evolutionary history of human ancestors. It is exactly for this reason that the study of Miocene apes is required.
The inclusion of Miocene apes in the analysis sheds a new perspective on the reconstruction of the LCA of humans and chimps. The fossil record clearly indicates that living hominoids constitute a narrow representation of an ancient radiation of more widely distributed, diverse taxa, none of which exhibits the entire suite of locomotor adaptations present in their extant relatives. Introducing Miocene apes into the equation allows us to understand that some modern ape similarities might have evolved in parallel in response to similar selection pressures. Early hominins originated in Africa from a Miocene LCA that does not match any living ape. Despite phylogenetic uncertainties, fossil apes remain key to reconstructing the “starting point” from which humans and chimps diverged. Future research should focus on fieldwork in new areas and methodological advances in morphology-based phylogenetics and paleoproteomics.
