Massive cranium from Harbin in northeastern China establishes a new Middle Pleistocene human lineage

It has recently become clear that several human lineages coexisted with Homo sapiens during the late Middle and Late Pleistocene.Here,we report an archaic human fossil that throws new light on debates concerning the diversification of the Homo genus and the origin of H.sapiens.The fossil was recovered in Harbin city in northeastern China,with a minimum uranium-series age of 146 ka.This cranium is one of the best preserved Middle Pleistocene human fossils.Its massive size,with a large cranial capacity(
1,420 mL)falling in the range of modern humans,is combined with a mosaic of primitive and derived characters.It differs from all the other named Homo species by presenting a combination of features,such as long and low cranial vault,a wide and low face,large and almost square orbits,gently curved but massively developed supraorbital torus,flat and low cheekbones with a shallow canine fossa,and a shallow palate with thick alveolar bone supporting very large molars.The excellent preservation of the Harbin cranium advances our understanding of several less-complete late Middle Pleistocene fossils from China,which have been interpreted as local evolutionary intermediates between the earlier species Homo erectus and later H.sapiens.Phylogenetic analyses based on parsimony criteria and Bayesian tip-dating suggest that the Harbin cranium and some other Middle Pleistocene human fossils from China,such as those from Dali and Xiahe,form a third East Asian lineage,which is a part of the sister group of the H.sapiens lineage.Our analyses of such morphologically distinctive archaic human lineages from Asia,Europe,and Africa suggest that the diversification of the Homo genus may have had a much deeper timescale than previously presumed.Sympatric isolation of small populations combined with stochastic long-distance dispersals is the best fitting biogeographical model for interpreting the evolution of the Homo genus.

Late Middle Pleistocene Harbin cranium represents a new Homo species

In eastern Asia,several Middle-Late Pleistocene human fossils,such as the Dali,Jinniushan,Hualongdong,and Harbin crania,evidently resemble each other and are phylogenetically closer to H.sapiens than to H.neanderthalensis or other archaic humans.1 The Harbin cranium is the best preserved of this group.It shows a mosaic combination of plesiomorphic and apomorphic features.Here,we suggest that the Harbin skull should be recognized as a new species of Homo.

Geochemical provenancing and direct dating of the Harbin archaic human cranium

As one of the most complete archaic human fossils,the Harbin cranium provides critical evidence for studying the diversification of the Homo genus and the origin of Homo sapiens.However,the unsystematic recovery of this cranium and a long and confused history since the discovery impede its accurate dating.Here,we carried out a series of geochemical analyses,including non-destructive X-ray fluorescence(XRF),rare earth elements(REE),and the Sr isotopes,to test the reported provenance of the Harbin cranium and get better stratigraphic constraints.The results show that the Harbin cranium has very similar XRF element distribution patterns,REE concentration patterns,and Sr isotopic compositions to those of the Middle Pleistocene-Holocene mammalian and human fossils recently recovered from the Harbin area.The sediments adhered in the nasal cavity of the Harbin cranium have a 87Sr/86Sr ratio of 0.711898,falling in the variation range measured in a core drilled near the Dongjiang Bridge,where the cranium was discovered during its reconstruction.The regional stratigraphic correlations indicate that the Harbin cranium was probably from the upper part of the Upper Huangshan Formation of the Harbin area,which has an optically stimulated luminescence dating constraint between 138 and 309 ka.U-series disequilibrium dating(n=10)directly on the cranium suggests that the cranium is older than 146 ka.The multiple lines of evidence from our experiments consistently support the theory that the Harbin cranium is from the late Middle Pleistocene of the Harbin area.Our study also shows that geochemical approaches can provide reliable evidence for locating and dating unsystematically recovered human fossils,and potentially can be applied to other human fossils without clear provenance and stratigraphy records.