New research suggests that a small but measurable share of human DNA may come from an unknown archaic lineage that once lived alongside our ancestors. The study indicates that these genetic traces appear in people across Africa and beyond, offering a fresh look at the complexity of human evolution.
A Hidden Chapter in Human History
For years, human origins were often described as a straightforward journey from Africa to the rest of the world. Genetic discoveries changed that picture by showing that modern humans mixed with Neanderthals and Denisovans. Now, researchers have identified signs of yet another ancient contribution -- one that has no confirmed fossil record and no sequenced genome.
Using a new method called TRACE -- short for Tracking Archaic Contributions via ARG Estimation -- scientists examined how DNA segments fit into ancestral family trees across the genome. Instead of comparing modern DNA only with known archaic genomes, the approach looks for unusually old branches and long inherited segments that suggest interbreeding with a deeply diverged population.
What the Analysis Revealed
The team applied TRACE to 503 genomes from the 1000 Genomes Project, including samples from Europe, East Asia, South Asia, West Africa and East Africa. The method successfully recovered known Neanderthal and Denisovan ancestry, while also detecting a separate signal in every population studied.
That signal was estimated to make up about 0.49% to 1.1% of the genome, depending on the group. The researchers say the pattern is consistent with a distinct archaic lineage rather than a branch of Neanderthals or Denisovans. They also found a deeper "super-archaic" genetic trace in Oceanians, pointing to an even older interaction in human history.
The findings, published in Science, do not close the case on who this lineage was, but they strengthen the idea that modern humans carry genetic echoes from multiple ancient populations. As genomic tools become more precise, the story of human ancestry may continue to expand in unexpected ways.
In the future, methods like TRACE could help map even more hidden layers of our shared biological past.
