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

• Main Authors: Xijun Ni, Qiang Ji, Wensheng Wu, Qingfeng Shao, Yannan Ji, Chi Zhang, Lei Liang, Junyi Ge, Zhen Guo, Jinhua Li, Qiang Li, Rainer Grün, Chris Stringer
• Format: Article
• Language: English
• Published: Elsevier 2021-08-01
• Series: The Innovation
• Subjects: human phylogeny; human cranium fossil; human dispersal; human diversification
• Online Access: http://www.sciencedirect.com/science/article/pii/S2666675821000552

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. Public summary: • More than 100,000 years ago, several human species coexisted in Asia, Europe, and Africa • A completely preserved fossil human cranium discovered in the Harbin area provides critical evidence for understanding the evolution of humans and the origin of our species • The Harbin cranium has a large cranial capacity (∼1,420 mL) falling in the range of modern humans, but is combined with a mosaic of primitive and derived characters • Our comprehensive phylogenetic analyses suggest that the Harbin cranium represents a new sister lineage for Homo sapiens • A multi-directional “shuttle dispersal model” is more likely to explain the complex phylogenetic connections among African and Eurasian Homo species/populations