Department of Anthropology, New Mexico State University, Las Cruces, NM 88003, USA.
Humans, Old World monkeys, gibbons, and the great apes of Africa and Asia are the only survivors of a highly diverse evolutionary radiation that began at least 28 million years ago (1, 2). The fossil record of human evolution after we diverged from apes is rich, but much less is known about the evolutionary history of modern apes. Not only is the fossil record incomplete but also the morphology of primitive apes from the Miocene (25 to 5 million years ago) seldom conforms to expectations based on living species. The ancestors of gibbons are particularly elusive. On page 528 of this issue, Alba et al. describe a Miocene fossil from Catalonia, Spain, that may bridge the gap between earlier small-bodied African apelike primates and living gibbons (3).