Proteins preserved in six teeth from China may offer a new clue to how ancient human groups met and mixed. A report by The Conversation’s Sally Christine Reynolds, an Associate Professor in Hominin Palaeoecology at Bournemouth University, describes a Nature study by Qiaomei Fu and colleagues. The researchers recovered protein information from Homo erectus fossils around 400,000 years old—fossils too ancient to yield usable DNA, according to the report.
The findings add detail to a picture of human evolution that is more tangled than a simple tree of separate branches. The report explains that researchers once often described ancient human relatives such as H. erectus as evolutionary dead ends, replaced by later populations. Evidence from ancient genomes has since shown that some lineages interbred. The new work offers a way to look further back in time, using proteins that can remain in tooth enamel after DNA has degraded.
The six teeth came from three Chinese sites: Zhoukoudian, Hexian and Sunjiadong. All shared a previously unknown amino-acid variant—a change at one position in a protein sequence—that the report says has not been found in other hominins, living or extinct. The variant groups the eastern Asian specimens together as H. erectus and, Reynolds writes, helps resolve debate about whether the unusual Hexian fossils belonged to that species.
A second variant shared by the teeth is also found in Denisovans, an archaic human group known mainly from a Siberian cave. The report says the corresponding genetic variant appears in living people, at a reported frequency of 21% in the Philippines and about 1% in India. Its distribution is described as consistent with an origin through Denisovan ancestry.
The proposed explanation is a chain of gene exchange: H. erectus populations in East Asia may have passed the variant to Denisovans, who later passed it to ancestors of some people in Southeast Asia and Oceania. The report calls this transfer between species introgression. The pathway is an interpretation of the evidence, rather than a directly observed encounter, and the report does not establish what the variant does in the body.
Reynolds places the finding alongside broader evidence for mixing among ancient human groups. The report notes, for example, that people outside Africa carry Neanderthal ancestry and that Papuans and Aboriginal Australians carry additional Denisovan ancestry. It also describes evidence for Denisovan-like ancestry in parts of Southeast Asia and Oceania, and genetic signatures from an unidentified archaic lineage in West African populations. These examples come from earlier research; the six teeth do not by themselves establish how common interbreeding was across human evolution.
The approach could also help investigate ancient populations for which DNA has not been recovered. The report mentions Homo floresiensis and Homo luzonensis as lineages whose remains have yielded no DNA and, until now, no molecular data. Whether either contributed genetic material to later populations remains unresolved. Protein evidence from teeth may offer another way to explore that question, but the report says the H. erectus-derived variant’s functional consequences are also unknown.
<a href="https://www.sciencedaily.com/releases/2026/11/261102202836.htm">Source: The Conversation report on ScienceDaily</a>