Everyone May Carry DNA From An Unknown Human Ancestor, New Study Suggests

A new study has found evidence that people around the world may carry DNA from an unknown group of ancient human relatives that scientists have never identified through fossils or ancient DNA.

Researchers from the University of California, Berkeley, and Johns Hopkins University developed a new method called TRACE to search for signs of ancient ancestry using only modern human genomes. Their findings were published in the journal Science.

Scientists already know that modern humans interbred with Neanderthals and Denisovans after migrating out of Africa. This has been confirmed through comparisons between ancient DNA and the genomes of people living today.

However, it has remained unclear whether the ancestors of modern humans also mixed with other ancient human groups in Africa before these migrations took place. The lack of preserved archaic DNA from sub-Saharan Africa has made this question difficult to answer.

To investigate, the research team analysed the genomes of 503 people from different populations around the world. They examined thousands of genetic family trees hidden within human DNA, looking for unusually old genetic branches that could point to ancient ancestry.

The study found that about 2 per cent of the DNA in non-African populations came from archaic human lineages, which matches previous research. Around half of this DNA could be linked to Neanderthals, while a smaller amount matched Denisovans.

The remaining genetic material, however, did not match any known ancient human genome. Researchers found between 0.5 and 1 per cent of DNA from what they describe as a "ghost" lineage. This unknown group appears to have split from the human family tree more than 500,000 years ago.

The mysterious ancestry was detected in every population studied. Researchers were particularly surprised to find it in parts of the genome that were previously thought to be uniquely modern human. One of these regions is located near FOXP2, a gene associated with speech and language.

Experts say the findings are promising but need further confirmation. Patrick F. Reilly, a computational biologist at Yale University who was not involved in the study, said that all scientific methods can produce false positives and that additional evidence will be needed.

Scientists hope future discoveries, including new fossils or advances in genetic analysis, will help determine whether this hidden lineage really existed. If confirmed, the findings could provide a new understanding of human evolution and reveal that our family tree is more complex than previously believed.