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The human family tree just became even more complicated.

Scientists have discovered genetic evidence of two previously unknown human lineages hidden within the DNA of people living today. Unlike Neanderthals and Denisovans, these mysterious ancestors have never been identified from a sequenced genome.

Instead, researchers worked backward from the DNA of modern humans to uncover evidence that our ancestors repeatedly encountered and interbred with other human groups.

The findings, published in the journal Science, suggest that human evolution was not a simple progression from one species to another. Instead, it was a tangled history of migrations, encounters and genetic mixing among numerous ancient human populations.

Scientists Discover Two “Ghost” Human Ancestors

Researchers from the University of California, Berkeley, and Johns Hopkins University identified evidence of two distinct ancient lineages.

Scientists refer to the first as a “ghost” lineage because there is currently no known fossil or sequenced genome that identifies the population responsible for the DNA.

The second is even older and has been described as a “super-archaic” lineage.

Neither represents a newly discovered species with a fossil skeleton. Instead, the evidence comes from genetic patterns preserved in modern human DNA.

That distinction is important: researchers have not recovered DNA directly from these mysterious ancestors. They have reconstructed their existence from the genetic history contained within living human genomes.

One Unknown Ancestor May Be Present in Everyone

The first ghost lineage appears to have interbred with the ancestors of modern humans in Africa more than 50,000 years ago, before the major expansion of Homo sapiens out of Africa.

Because the genetic exchange happened so early, the resulting DNA appears to have spread widely as modern humans migrated around the world.

Researchers estimate that this ghost lineage contributes roughly 0.5% to 1% of the genome of an average modern human.

That is surprisingly comparable to the amount of Neanderthal ancestry found in many modern populations.

The researchers estimate that this mysterious lineage separated from the lineage leading to modern humans approximately 800,000 years ago. That timing overlaps with a major period of diversification among ancient human populations.

An Even Older Human Relative Left a Genetic Trace

The second discovery is even more remarkable.

Researchers found evidence of a super-archaic lineage that separated from other human lineages roughly 1.8 million years ago.

This ancient population apparently did not contribute its DNA directly to modern humans.

Instead, the researchers propose that the super-archaic lineage first interbred with Denisovans in Eurasia, probably more than 200,000 years ago.

Later, Denisovans interbred with Homo sapiens. Some of the super-archaic genetic material was therefore passed along through the Denisovans and eventually entered modern human populations.

In other words, part of our DNA may contain a genetic echo of a human lineage that lived more than a million years ago.

What Is a “Ghost Ancestor”?

The term ghost ancestor does not mean scientists have discovered a literal ghost species.

In genetics, a ghost lineage refers to an ancestral population that is inferred from genetic evidence but has not yet been identified through fossils or a directly sequenced genome.

Scientists already know that Neanderthals and Denisovans contributed DNA to modern humans because researchers have recovered and sequenced ancient DNA from those populations.

The newly identified lineages are different.

Researchers can see their genetic fingerprints, but they don’t yet know exactly which ancient human populations produced them.

The mysterious groups could potentially be related to Middle Pleistocene human populations in Africa or ancient Eurasian populations such as Homo erectus, but researchers emphasize that their identities remain uncertain.

A New Method Revealed the Hidden DNA

The discovery was made possible by a computational technique called TRACE, short for TRacking Archaic Contributions via ARG Estimation.

Rather than requiring a fossil containing preserved DNA, TRACE examines the genealogical relationships among DNA sequences in modern humans.

The researchers used complete genomes from people around the world and reconstructed ancestral recombination graphs, which essentially map how sections of DNA are related through generations.

Some DNA regions have unusually deep ancestry. If a particular section appears to have remained separated from the main human lineage for an exceptionally long time before entering the modern human gene pool, it can provide evidence of ancient interbreeding.

TRACE was able to identify known Neanderthal and Denisovan ancestry, providing a way to test the method before using it to search for previously unknown lineages.

Human Evolution Looks More Like a Web Than a Tree

For decades, human evolution has often been illustrated as a branching family tree.

But discoveries involving Neanderthals, Denisovans and now additional unidentified populations suggest that the picture is considerably more complicated.

Ancient human groups separated from one another, migrated into new regions, encountered other populations and sometimes interbred.

The result was not a series of completely isolated branches.

It was more like a genetic web, with DNA moving between populations at different points in prehistoric history.

The Berkeley researchers say these findings reinforce the idea that mixing among ancient human populations was widespread over evolutionary timescales.

Modern Humans Carry More Archaic DNA Than We Once Thought

The researchers estimate that roughly 2% of the modern human genome comes from archaic hominins when the various identified and inferred contributions are considered.

The newly identified ghost ancestry appears in both African and non-African populations, supporting the idea that the interbreeding event occurred before the major expansion of Homo sapiens out of Africa.

The second, super-archaic signal is particularly interesting in populations from Oceania, where some groups carry relatively high levels of Denisovan ancestry.

The researchers found the deep genetic signal within Denisovan-related regions, supporting the idea that this extremely ancient DNA reached modern humans through Denisovan populations.

Could These Ancient Genes Have Helped Humans Survive?

The genetic material isn’t necessarily just evolutionary baggage.

Researchers found that some archaic DNA segments are enriched in genomic regions associated with immune and metabolic functions.

That could make evolutionary sense.

When ancient humans encountered new environments, they also encountered unfamiliar pathogens, foods and other environmental challenges. Interbreeding with other human populations could have introduced genetic variations that later proved useful.

Natural selection may then have favored some of those inherited variants.

However, researchers caution that identifying a genetic segment as archaic does not automatically mean it provided a survival advantage. More research will be needed to determine exactly what these inherited sequences do.

Why Haven’t Scientists Found These Ancestors?

One of the biggest mysteries is why researchers have genetic evidence without an identified fossil or genome.

Ancient DNA is extremely difficult to preserve. Temperature, moisture, soil chemistry and time can all destroy genetic material.

Many ancient humans likely left behind few fossils, while others may have lived in environments where preservation was poor.

That means the fossil record is inevitably incomplete.

The new research demonstrates that scientists may be able to reconstruct parts of human history even when the physical evidence has disappeared.

Modern DNA can effectively serve as a genetic archive of encounters that occurred hundreds of thousands or even millions of years ago.

Could We Discover More Unknown Human Ancestors?

Researchers believe the answer could be yes.

As scientists analyze larger and more geographically diverse collections of human genomes, they may uncover additional genetic signals from populations that have never been identified in the fossil record.

The discovery of more Denisovan genomes could also help researchers understand the super-archaic contribution in greater detail.

The Berkeley team believes TRACE could potentially identify weaker signals from other lost human populations as genomic datasets become more comprehensive.

What This Discovery Means for Human Evolution

The discovery of two unknown human ancestors doesn’t rewrite everything scientists know about human evolution.

Instead, it fills in another piece of an increasingly complicated puzzle.

We already knew that modern humans inherited DNA from Neanderthals and Denisovans. Now there is evidence that our ancestors also interacted with other populations whose identities have been lost to time.

One lineage may have contributed DNA directly to the ancestors of everyone alive today.

Another may have left its genetic mark indirectly through Denisovans.

And there could be even more lost populations waiting to be discovered.

The Bottom Line

Traces of two unknown human ancestors have been detected in modern human DNA, providing another remarkable glimpse into humanity’s deep evolutionary history.

The first mysterious lineage appears to have mixed with early Homo sapiens in Africa more than 50,000 years ago and may account for roughly 0.5% to 1% of the DNA carried by modern individuals.

The second lineage is much older, dating back roughly 1.8 million years, and appears to have passed its genetic material into modern humans through Denisovans.

Most importantly, scientists made the discovery without having a sequenced genome from either mysterious population.

The findings show that our DNA contains clues to human history that scientists are only beginning to decode. As genetic analysis becomes more sophisticated, the genomes of people alive today could reveal additional chapters about human relatives whose fossils—and even whose names—have been lost forever.

The human family tree may not really be a tree at all. It may be a vast genetic network, and we are still discovering the connections.

Editor’s Note: This article is based on research published in the journal Science in 2026. The identities of the two inferred ancestral populations remain unknown, and researchers’ proposed connections to ancient human groups such as Middle Pleistocene Homo and Homo erectus are possibilities rather than confirmed identifications.