They could not have had any clue that they were doing it, but, through their dining habits, prehistoric predators helped create the hominin fossil record. From the croc-bitten feet of Homo habilis to the hapless Homo erectus of Dragon Bone Hill and the chewed-up remains of Orrorin, many well-known hominin specimens were either killed or scavenged by carnivores of various stripes. Today, in a poster presented at the 70th annual Society of Vertebrate Paleontology meeting, University of Minnesota researcher Kirsten Jenkins goes back even further to document how earlier apes fell prey to various archaic carnivores.
Between 20 and 16 million years ago, Kenya’s Rusinga Island hosted a lush forest. Thanks to the work of numerous anthropologists – Arthur Hopwood, Louis Leakey, Mary Leakey, and Alan Walker among them – we know that this place was home to a variety of apes which lived alongside one another, including Proconsul and Dendropithecus. This place was not an ape Eden, though. As ascertained by Jenkins, many of the the primate bones found on Rusinga bear various scratches, pits, and other damage indicative of predation. As with many hominin sites, it appears that predators had helped create the primate fossil record on Rusinga, too.
The primary culprits were archaic mammalian carnivores called creodonts. With elongate, boxy skulls full of formidable teeth, these animals were the dominant predators before carnivores of more modern aspect underwent their own radiation. Jenkins is reluctant to “go from toothmarks to taxa”, but the overall damage to the ape bones is consistent with what creodonts found on Rusinga were capable of. Based upon the pattern of damage, it appears that the creodonts mostly defleshed the bodies of the apes and gnawed off the ends of bones to get at the marrow inside, but did not crush through bones the way spotted hyenas do today. Furthermore, there appears to be some indication that predatory birds occasionally fed on the apes – just as extant raptors feed on monkeys – but the identity of the avian attacker is also unknown.
The results as still preliminary, but Jenkins’ poster is consistent with the hypothesis that predators have played a significant role in shaping the evolution of their primate prey. Unfortunately we can’t observe Proconsul and its creodont predators like we can watch baboons and leopards today, but discoveries such as this help provide the wider context for what we know about primate evolution. Now that paleontologists know what to look for, I wonder how many other carnivore-damaged fossil primate bones are going to turn up.
Image: A drawing of the restored skull of Dissopsalis carnifex, a creodont from the Miocene of Kenya. From Wikipedia.