Ancient skulls belong to unknown species that preceded the Neanderthals
A new analysis of ancient skulls retrieved from a deep bone pit in the Atapuerca Mountains of northern Spain, suggests they belong to an unknown species that has characteristics of Neanderthals, as well as early members of the hominid lineage. The study provides further evidence for the intermingling of ancient species and the murky origins of our closest relative.
The study, which is published in the journal Science, was conducted by a team of Spanish paleoanthropologists who analysed 17 ancient skulls dating back 430,000 years. They came from the Sima de los Huesos (“pit of bones”) at Atapuerca, which offers the largest trove of hominid fossils ever found, including bones from 28 individuals. Prior to dating or examining the fossils, many researchers expected the remains to belong to a species called Homo heidelbergensis, which lived around 500,000 to 1 million years ago, and was a common ancestor to both Neanderthals and modern humans. But the results revealed something different.
The results showed facial features that were similar to Neanderthals, and typically observed in much younger fossils, such as robust lower jaws, small teeth at the rear of the jaw, and thick brow ridges. However, they also had relatively small brains and other primitive features, which suggests they were distinct from Neanderthals, perhaps early members of the lineage.
Facial reconstruction of a Neanderthal showing pronounced brow ridge. Photo source .
The physical features of the Sima fossils suggest these hominins were part of the Neanderthal lineage, but not necessarily direct ancestors. Indeed, other ancient humans in Europe do not exhibit the suite of Neanderthal-like features seen in the Sima fossils, suggesting more than one evolutionary lineage appears to have coexisted on that continent at the time. The Atapuerca team suggests that the bones be reclassified as a new, still unnamed species that was an ancestor of Neanderthals, but not modern humans.
Newly proposed lineage map. Photos: Robert Clark. Source: Matthias Meyer, Max Planck Institute, and Juan Luis Arsuaga, Universidad Complutense de Madrid
Scientists still debate whether Neanderthals and modern humans are distinct and separate species. Neanderthals were generally shorter and stockier than modern humans, and Neanderthal skulls display large brows and jaws, big noses, sloping foreheads and chins, and long, flat brainpans. Still, Neanderthals remained closely related enough with modern humans for the two to interbreed — in fact, about 1.5 to 2.1 percent of the DNA of any modern human outside Africa is Neanderthal in origin.
Paleoanthropologist Chris Stringer of the Natural History Museum in London agrees that the Sima fossils are ancestral only to Neanderthals, not modern humans, but questions the date and classification of the find. He thinks the fossils may be younger and suggests simply calling them early or archaic Neanderthals.
While the latest findings are vitally important in the quest to piece together the mysteries of human origins, they also serve to raise more questions than answers. Research over the last two years has shown us just how complex our ancient origins really area, and no ‘family tree’ can accurately describe the complicated intermingling that occurred millennia ago among different hominid species. Moreover, scientists are aware that there are traces of species in the DNA record, which are still completely unknown.
Featured image: This skull found in a cave in Spain provides clues as to how and when Neandertals evolved. Credit: Javier Trueba / Madrid Scientific Films