New Human: H. Naledi
The fossils exhibit a combination of primitive features that bring to mind our ancient australopithecine predecessors (including Lucy and her ilk) and features that are associated with Homo. For instance, the pelvis has a flared shape like that seen in Australopithecus, whereas the leg and foot resemble those of Homo sapiens. Likewise, the skull combines a small braincase with a cranium that is otherwise built like that of early Homo. The teeth, meanwhile, are small like those of modern humans, yet the third molar is larger than the other molars--a pattern associated with australopithecines. And the upper limb pairs an Australopithecus-like shoulder and fingers with a Homo-like wrist and palm. "All that combined leaves us with a really, really strange creature," Berger remarks.
Are they sure they didn't just mix up the bones? Remember when they put the iguanodon's thumb on its nose by mistake?
The mix-and-match anatomy of the H. naledi bones is not the only puzzling aspect of this discovery, however. At other fossil sites in the Cradle of Humankind, fossils are encased in sediment and animal bones are found mixed in with the human remains. The bones of humans and animals alike accumulate in the caves there through catastrophic events such as falling down a hole in the ground into an underground cave and getting trapped, or becoming dinner for the large carnivores that denned in the caves. But the Rising Star bones are not encased in sediment, nor do any remains of any vertebrate animals, apart from a few rodents and birds, accompany them. Given the absence of any evidence to indicate that Homo naledi fell or washed into the underground chamber or was transported there by a predator, the discovery team suggests that this small-brained human deliberately disposed of its dead. Furthermore, the location of the H. naledi bones in a chamber that appears to have always been lightless and difficult to access suggests that the humans went to great lengths to deliver the bodies there, and possibly needed an artificial light source (perhaps a simple torch) to do so. The behavior is important because it implies that H. naledi had, as Hawks puts is, "a shared cultural knowledge of mortality."
Not every paleoanthropologist is ready to believe the burial ground theory just yet. And they still haven't managed to date the bones, so that's a mystery.
For his part, Hawks notes that the behavioral insights from Rising Star hint at an interesting parallel to the anatomical story. "We have all these things we think of as human. From an anatomy point of view walking upright is human, a large brain is human, tool-making hands are human. But all of these things happened at different times in different ancestors. The package we think of as human did not appear simultaneously," he observes. "I don't know why we would think behavior is any different--a package evolved and different parts appeared at different times."
By min | September 10, 2015, 8:46 AM | Science