Researchers say an almost complete archaic human cranium recovered from the Middle Pleistocene of northeastern China suggests a new sister lineage for Homo sapiens.
The international study argues that the beautifully preserved fossil provides critical evidence for understanding the evolution of humans and the origin of our species.
More than one hundred thousand years ago, several human species coexisted in Asia, Europe and Africa. In China, a few archaic human fossils such as those from Dali, Jinniushan and Hualongdong show a mosaic combination of primitive and derived features. There has long been fierce debate about whether these archaic fossils belong to different species of human, might be transitional forms between the earlier species Homo erectus and Homo sapiens, or might actually represent primitive forms of our own species H. sapiens.
The cranium was reportedly discovered in 1933 when a bridge was built over the Songhua River in Harbin City. Because of its unsystematic recovery and the long time interval, information about the exact site and fossil layer was lost. Researchers used sophisticated geochemical analyses, including rare earth elements, strontium isotopic ratios and X-ray fluorescence, and direct Uranium series dating on the cranium.
Geochemist and team member Dr. Junyi Ge from the Chinese Academy of Sciences (CAS) said: “Although it is impossible to pin the cranium to an exact location with currently available technology, all the evidence suggests that it was from a bed of water-laid sediments aged between 138 and 309 thousand years ago in the Harbin region.’ Geochemist and team member Dr. Qingfeng Shao from the Nanjing Normal University added, ‘We are quite confident now that the fossil is older than 146 thousand years.”
Professor Chris Stringer Research Leader at the Natural History Museum in London said: “The Harbin cranium is huge, showing either the largest or second largest values for many measurements in our comparative fossil database, and its brain volume at ~1420 ml matches that of modern humans. It also shows other features resembling our species. It has flat and low cheekbones with a shallow canine fossa, and the face looks reduced and tucked under the braincase.”
Immense in size and presenting both primitive and derived features make the Harbin cranium quite distinct. It is so distinctive that Prof Ji and some of his colleagues have even suggested naming the Harbin cranium as a new species of the genus Homo. They have called it “Dragon Man” (Homo longi). The name is derived from the geographic name, Long Jiang, or Dragon River, for the Heilongjiang Province.
Palaeoanthropologists usually compare morphological features one by one, or use landmark-based statistical analyses to evaluate overall similarities among compared human fossils. Prof Ji and his colleagues, however, decided to apply phylogenetic analyses in their research. Phylogenetic analyses are widely used in evolutionary biology and can include a set of mathematical techniques to establish branching diagrams to represent the evolutionary history or relationship between different species or organisms that have developed from a common ancestor.
The comprehensive phylogenetic analyses of Ji’s team reveal that the Harbin cranium and some other East Asian archaic human fossils, such as Dali, Jinniushan, Hualongdong and the Xiahe jawbone from the Tibetan plateau, belong to an evolutionary clade that shares the same last ancestor with Homo sapiens, our own species.
Prof Stringer continues: “It’s widely believed that the Neanderthals form the sister group of the sapiens lineage. But our analyses suggest that the Harbin cranium and some other Middle Pleistocene human fossils from China form a third East Asian lineage, which is actually closer to sapiens than the Neanderthals are’. Thus, the excellent preservation of the Harbin cranium throws new light on the evolution of the genus Homo. ‘It’s estimated Middle Pleistocene age places it as an Asian contemporary of the evolving H. sapiens, H. neanderthalensis and Denisovan lineages. It may even be a representative of the enigmatic Denisovans, but that is something for the next stages of research.”
Source: Natural History Museum
Photo Credit: Kai Geng