When the first draft of the Neanderthal genome was published in 2010, researchers found that most people with recent ancestry outside Africa carry roughly 1 to 4 percent Neanderthal DNA. A human group whose physical traces vanished around 40,000 years ago still survives, in fragments, inside the cells of billions of people alive today.
It is one of the stranger findings in modern genetics.
Most of what we call extinction is binary. A species is gone, or it isn’t. The Neanderthal case is more complicated than that, and what the genetic record now shows sits uneasily with the word “extinct” itself.
What the 2010 paper actually said
The paper, A Draft Sequence of the Neandertal Genome, was published in Science by Richard Green and colleagues at the Max Planck Institute for Evolutionary Anthropology in Leipzig, working with collaborators across more than thirty institutions. The DNA came from three individuals whose bones had been recovered from Vindija Cave in Croatia. The reconstructed genome was assembled from roughly four billion nucleotides drawn together from fragments tens of thousands of years old.
The finding that drew the most attention was that present-day non-Africans share more genetic variants with Neanderthals than present-day sub-Saharan Africans do. The most parsimonious explanation, the authors wrote, was a small amount of gene flow from Neanderthals into the ancestors of non-Africans, occurring shortly after the dispersal out of Africa and before non-African populations diverged from each other.
The researchers framed the signal carefully. The inherited pieces were small and scattered across the genome. The point was not that any particular Neanderthal trait had survived intact in modern humans. The point was that gene flow had happened, and that it had left traces a paper could measure.
What the picture looks like fifteen years later
The 1 to 4 percent figure has held up broadly. The more interesting part of the story is in the refinements.
In 2020, a Princeton-led team published a paper in Cell, Identifying and Interpreting Apparent Neanderthal Ancestry in African Individuals, that pushed back against the assumption that Africans had no Neanderthal DNA. Using a new method called IBDmix, Joshua Akey and his colleagues identified an average of around 0.3 percent Neanderthal ancestry in the African individuals they sampled. Roughly half of that signal, in their reading of the data, was best explained by back-migrations of Europeans into Africa over the past 20,000 years. The remainder may reflect earlier gene flow in the other direction: from an earlier modern-human population that left Africa, into Neanderthals, before that early dispersal disappeared.
The same paper revised the long-held belief that East Asians carried about 20 percent more Neanderthal DNA than Europeans. The actual figure, in their reading, was closer to 8 percent. The difference matters less than the reason. Previous estimates had used African populations as a reference assumed to contain no Neanderthal DNA, which it turned out they did, in small amounts.
The picture, in short, is messier than the 2010 paper suggested. The 1 to 4 percent figure remains the headline number for non-Africans. But the clean old split, with Neanderthal DNA outside Africa and none inside, no longer holds. Modern human populations carry Neanderthal sequence in different proportions and through different historical routes.
What the inherited DNA actually does
This is where the careful reader has to slow down.
A range of studies has looked at whether the small amount of Neanderthal DNA in modern genomes affects health, traits, or disease risk in living people. The most cited is a 2016 paper in Science by Corinne Simonti, John Capra and colleagues, The phenotypic legacy of admixture between modern humans and Neandertals, which compared Neanderthal-derived variants against the electronic health records of around 28,000 adults of European ancestry. The team reported associations between specific Neanderthal-derived sequences and conditions including skin lesions, blood coagulation, mood disorders, and immune response.
The word in that sentence to take seriously is “associations.” None of these are clean causal stories. A Neanderthal-derived variant near a gene linked to circadian rhythm, for example, showed an association with mood-related diagnoses in one dataset. The authors hypothesise a connection to light exposure at higher latitudes, where the Neanderthal lineage had spent hundreds of thousands of years adapting. They do not claim that Neanderthal DNA causes any particular condition. They report statistical associations in a particular dataset, with one possible evolutionary frame around them.
More recent work, including modelling from Sriram Sankararaman’s group at UCLA, has emphasised that the bulk of Neanderthal DNA in modern humans appears to have been mildly deleterious, and has been gradually selected against over the past 50,000 years. What remains is what was tolerated, or what conferred some adaptive value, or what was small enough to escape efficient removal.
What “extinct” turns out to mean
What we keep coming back to, in our reading, is how the word “extinct” handles all of this.
Neanderthals as a population are gone. There is no breeding group of Homo neanderthalensis anywhere on Earth. The full Neanderthal body form, the combination of features archaeologists recognise in the fossil record, has not continued as a living population. By any ordinary measure of species survival, they are absent.
And yet the genetic contribution persists, and in some cases it does something. Some of that inherited material is being expressed, right now, in the immune systems and skin cells and circadian rhythms of people who have never thought about Neanderthals once in their lives.
One framing some researchers use is that Neanderthals were not simply exterminated, but partly absorbed. The interbreeding with Homo sapiens happened over several thousand years across the regions where the two populations overlapped. Whatever drove the Neanderthal lineage to disappear as a distinct group, and the latest evidence suggests several factors in combination, the genetic record shows that a non-trivial portion of that lineage was simply taken into the surviving population.
Genetic traces of Denisovans, another archaic human population identified from a finger bone in a Siberian cave in 2010, are present at varying levels in living people in Oceania and parts of East Asia. The Neanderthal case is the clearest available example of this kind of half-survival, but it is unlikely to be the only one.
The harder question
The harder question is what to make of any of this, if anything.
We are writers, not geneticists or evolutionary biologists. We have no findings of our own to offer. What we can say is what fifteen years of careful reading in the field has shown.
The Neanderthal who walked into a Sapiens band in the cold steppe of what is now Hungary or southern France, 50,000 years ago, did not know they were on the losing side of a long demographic story. They did not know that their lineage as a recognisable population would be over within a few hundred generations. They did not know that fragments of their genome would still be being copied, cell by cell, in a parent in Saigon or a graduate student in Toronto in 2026.
It is not a comforting story. It is not a tragic one either. It sits oddly with both frames.
The species ended. The DNA didn’t.
The two facts are both true.
