An international team of scientists has discovered an ancient human fossil in China that defies classification within the existing human family tree. The fossil, known as HLD 6, was found in Hualongdong, East Asia, in 2019 and has since baffled experts at the Chinese Academy of Sciences (CAS), who have been unable to correlate it with any known family tree.
HLD 6’s unique characteristics have left scientists baffled. While its facial structure resembles that of modern humans, the lack of a chin is reminiscent of the extinct Denisovans, an ancient species that parted ways with Neanderthals more than 400,000 years ago. This suggests the need for an additional branch in our current view of the human family tree.
In collaboration with researchers from China’s Xi’an Jiaotong University, the University of York (UK) and Spain’s National Research Center for Human Evolution, CAS scientists suggest that HLD 6 represents an entirely new family tree – a hybrid between the branch that gave rise to modern humans and the branch that gave rise to other ancient hominins in the region, such as the Denisovans.
Finds of hominin fossils in China have historically caused difficulties in categorizing them. These remains often do not fit into established lineages and are sometimes seen as intermediate variants on the path to modern humanity. However, this linear interpretation is controversial and not widely accepted.
Previous genomic studies of Neanderthal remains in Europe and western Asia have hinted at the existence of a fourth hominin lineage during the Middle and Late Pleistocene. However, this missing group has never been formally identified in the fossil record. Recent finds in China may be the missing piece of this evolutionary puzzle.
The fossilized jaw and skull of HLD 6 belong to a 12-13 year old human. While the facial features resemble those of modern humans, the limbs, skull cap and jaw have more primitive features. This mosaic of physical characteristics complicates understanding the path to modern humans and confirms the coexistence of three lineages in Asia: Homo erectus, Denisovans, and a recently discovered lineage closely related to us.
The appearance of Homo sapiens in China about 120,000 years ago suggests that some of our “modern” traits existed in the region long before that. It is possible that the last common ancestor of Homo sapiens and Neanderthals originated in Southwest Asia and then spread to all continents. However, further archaeological research is needed to confirm this theory.
The findings, published in the Journal of Human Evolution, shed new light on human evolution and challenge our current beliefs about ancient origins. As scientists continue to discover new information about our past, the human family tree may undergo further revision, revealing the complexity and diversity of our evolutionary history.