A tooth to confuse them all: unclassifiable human remains discovered

A group of researchers from the National Center for Research on Human Evolution (CENIEH) have recently published in the Journal of Human Evolution an analysis of some 21 ancient teeth from the Hualongdong site in Anhui province, estimated to be around 300,000 years old. The dental remains display an unusual combination of modern and archaic features, challenging traditional classifications of human evolution in Asia.

The fossil set was recovered from caves discovered in 2006 , with archaeological work unearthing up to 16 individuals to date. The most significant specimen, coded HLD 6, corresponds to an adolescent of about 13 years of age and offers a curious mix of morphologies : a relatively modern face, without a defined chin, and a thick mandibular bone like that of Homo erectus.

The new study, led by Professor Wu Xiujie and other leading team members , concludes that these teeth do not fit into either classic Homo erectus or Homo sapiens , and likely represent a hybrid or distinct evolutionary line, overlapping with known hominins. According to the authors, the tooth exhibits traits shared with Neanderthals and Denisovans , but cannot be confidently assigned to any identified species.

The tooth exhibits traits shared with Neanderthals and Denisovans, but cannot be assigned to any identified species.

The combination of morphological characteristics—such as a thin-walled jaw (modern human) and archaic mandibular features —suggests the possibility of crossbreeding between sapiens and erectus in Asia. Therefore, the conclusions point to a previously unknown hybridization between species in human evolution. "It's a mosaic of traits never seen before, almost as if the evolutionary clock were ticking at different speeds in different parts of the body," said study co-author María Martinón-Torres , a paleoanthropologist at the National Center for Research on Human Evolution (CENIEH) in Spain, in a statement, Live Science reports.

This discovery complicates the " Out of Africa " narrative by suggesting that there may have been persistent indigenous lineages in Asia that interacted and interbred with African migrants before 200,000 years ago. The chronology of the site, validated through radiometric dating, places these remains in the middle Pleistocene, a timeframe compatible with other finds such as Homo juluensis.

The scientific community has greeted the report with wide-eyed anticipation; several experts believe it opens up a new layer of uncertainty about how various human lines coexisted in Central and East Asia for hundreds of thousands of years .

The study also adds weight to previous hypotheses that suggested genetic interactions between Denisovans and local populations in Asia, contributing to the debate about the existence of yet-to-be-identified ghost lineages. In the absence of recoverable DNA, teeth and jaws remain the main clues for reconstructing this complex evolutionary framework.