Every person alive today may be carrying genetic fragments inherited from a human population scientists have never identified.
And that is only one of them.
Researchers have uncovered traces of two previously unidentified extinct human lineages buried inside modern genomes, revealing evidence of ancient interbreeding that happened tens or even hundreds of thousands of years before recorded history.
One of these populations appears to have mixed directly with the ancestors of modern humans in Africa before the major migration of Homo sapiens out of the continent. The other belonged to an even older lineage whose genetic material reached us indirectly through Denisovans.
The discovery, published in Science, adds another complication to an increasingly crowded human family tree.
Except it is becoming difficult to call it a tree at all.
Scientists found ancestors without finding their bones
Usually, identifying DNA from an extinct human population requires ancient remains.
That is how researchers established that modern humans interbred with Neanderthals and Denisovans. Scientists extracted genetic material preserved in ancient bones and compared those genomes with DNA from people alive today.
The new research did something very different.
Researchers developed a computational method called TRACE, short for Tracking Archaic Contributions via Ancestral Recombination Graph Estimation.
Instead of starting with ancient DNA, TRACE works backwards from modern genomes.
The technique reconstructs genealogical relationships between sections of DNA and searches for regions with ancestry that extends unusually far into the past. Those exceptionally old genetic branches can reveal contributions from populations whose genomes have never been sequenced.
When the researchers tested the method, it successfully rediscovered known Neanderthal ancestry. In populations from Asia and Oceania, it also identified known Denisovan genetic material.
Then it found something else.
Large numbers of ancient DNA segments matched neither.
Around 1% of your genome may come from a mystery population
The first unidentified lineage appears to have separated from the ancestors of modern humans around 800,000 years ago.
Much later, descendants of that lineage interbred with early modern humans in Africa, before the most recent major expansion of Homo sapiens out of Africa more than 50,000 years ago.
That timing produced an extraordinary consequence.
The ancestry is not confined to one modern population.
Researchers detected it in both Africans and non-Africans, meaning the genetic contribution occurred early enough to become part of the ancestry ultimately carried across the world.
Each person today may have approximately 0.5% to 1% of their genome inherited from this unidentified group. The researchers estimate that archaic hominins collectively account for roughly 2% of the modern human genome.
That puts the contribution from this unknown population in roughly the same order of magnitude as Neanderthal ancestry in many people.
Yet scientists do not know who these humans were.
The second ancestor is much older
The second signal reaches even further into the past.
Researchers identified what they describe as a super-archaic lineage that appears to have diverged approximately 1.8 million years ago.
This population did not pass its genes directly to modern humans.
Instead, it appears to have interbred with Denisovans in Eurasia. Denisovans later interbred with Homo sapiens, allowing a small quantity of this far older DNA to make a second genetic journey into people living today.
Denisovans themselves may have inherited around 3% to 5% of their genome from this super-archaic population. Only a fraction of that DNA subsequently reached modern humans.
The identity of the population remains unknown.
Its estimated age overlaps with the period during which Homo erectus and other early human populations existed in Eurasia, but that does not prove the DNA came from Homo erectus. Without a matching ancient genome, assigning a species name would go beyond the evidence.
Human evolution is looking less like a tree
The traditional illustration of human evolution usually resembles a branching tree.
One ancestral population divides into two. Those divide again. Eventually one branch leads towards modern humans while others end with extinct relatives such as Neanderthals.
Genetics has steadily dismantled that tidy picture.
Modern humans interbred with Neanderthals.
They interbred with Denisovans.
Neanderthals and Denisovans also exchanged genes with other populations, and the new study indicates that modern genomes preserve contributions from still more human groups whose identities remain unknown.
Human evolution increasingly resembles a network in which populations separated, encountered one another again and exchanged genes repeatedly.
Extinction therefore did not always mean disappearance.
A population could vanish physically while fragments of its genome survived inside descendants of another human group.
Some of that ancient DNA may still matter
These inherited fragments are not distributed randomly.
Researchers found archaic ancestry in genomic regions associated with functions including immunity and metabolism.
There is an evolutionary reason this could happen.
When human populations moved into new environments, they encountered unfamiliar foods, climates and diseases. Interbreeding with people who had already lived in those environments could introduce useful genetic variation.
If one of those inherited variants helped descendants survive or reproduce, natural selection could preserve it for thousands of generations.
That means an encounter between two human populations in deep prehistory could, in principle, still influence biology today.
The study does not establish what each newly identified genetic segment does, and carrying archaic ancestry should not be interpreted as dividing modern humans into different biological categories.
In fact, one of the most striking findings points in precisely the opposite direction.
The first ghost lineage contributed ancestry before modern humans expanded widely beyond Africa.
Its genetic traces therefore became part of a heritage shared across humanity.
There may be more ghosts left to find
The two unidentified lineages may not be the final additions.
TRACE depends on having enough modern genomes to reconstruct ancient genealogical patterns. As genetic databases become larger and more representative of populations around the world, weaker signals from other extinct groups may become detectable.
That is particularly important in Africa.
The continent contains the greatest human genetic diversity and the deepest history of Homo sapiens, yet ancient DNA preservation is often more difficult in warm environments than in colder regions where many famous Neanderthal and Denisovan remains have been recovered.
Computational methods that can reconstruct lost ancestry from living people therefore offer another way of investigating deep African human history even when ancient DNA is unavailable.
The result changes what a missing fossil means.
Scientists may never recover a usable genome from some of the human populations that once lived alongside our ancestors.
But those populations may not have disappeared completely.
Part of them could already be sitting inside us.
Source Information
Study Title: Recovering signatures of archaic hominin introgression using ancestral recombination graphs
Authors: Yulin Zhang, Arjun Biddanda, Sarah A. Johnson, Colm O’Dushlaine and Priya Moorjani
Journal: Science
Published: 30 July 2026
DOI: 10.1126/science.aef8874
