The Fossil Record and Evolutionary History of Hylobatids

Abstract

The fossil record documenting the evolution of hylobatids is extremely poor, so details of their phylogenetic and geographic origins and subsequent evolutionary history are obscure. Based on molecular clock estimates, hylobatids diverged from other hominoids during the early Miocene , at ~19 Ma, and crown hylobatids originated at ~8 Ma. The oldest fossil hylobatid is Yuanmoupithecus from the late Miocene of China, dating to ~7–9 Ma, which represents the primitive sister taxon of crown hylobatids. The molecular and paleontological evidence indicates that there was a ghost lineage for the initial 10 myrs of hylobatid evolutionary history, with no trace of a fossil record. Hylobatids presumably originated in Africa during the early Miocene, but the timing of their arrival in Asia and their early geographic distribution is unknown. Since there are no suitable fossil precursors for Yuanmoupithecus at older sites in China, it is likely that stem hylobatids migrated northwards from Southeast Asia during the late Miocene, but the Neogene fossil record from this region is poorly documented. Hylobatids occur at a number of Pleistocene archaeological and paleontological sites throughout southern China and Southeast Asia, but they tend to be relatively rare elements of the primate fauna. These are generally referable to extant lineages and species, except for Bunopithecus sericus from the early or middle Pleistocene of China. This contribution reviews what is known about the evolutionary history of the hylobatids based on the fossil evidence, but since there is much that we do not know and cannot deduce about the phylogeny of hylobatids from the incomplete fossil record, a fuller appreciation of the evolutionary history relies on what can also be learned from comparative anatomy and molecular data.