Neanderthal DNA is still with us. If your ancestors came from outside Africa, a small slice of your genome, typically a percent or two, descends from a population of humans who vanished from the fossil record roughly 40,000 years ago. That fact is no longer in dispute. What remains open is how much those inherited pieces matter for health and biology, and the honest answer is that they matter in specific, limited ways that researchers are still sorting out.

This guide covers how the DNA got there, how much of it people carry, what it seems to do, and which claims in popular coverage run ahead of the evidence.

How do we know humans and Neanderthals interbred?

The proof is in the genomes. In 2008 researchers published a complete Neanderthal mitochondrial genome, and in 2010 the first draft of the nuclear genome appeared. Comparing it to people alive today showed that Europeans and Asians share more genetic variants with Neanderthals than Africans do. Interbreeding was the simplest explanation, and later genomes confirmed it. Further high-quality Neanderthal genomes came from the Altai Mountains, Vindija Cave in Croatia, Chagyrskaya Cave and elsewhere over the following decade.

The pattern is not a quirk of one method. Different analyses, run on different genomes, point the same way. Neanderthals and modern humans were close enough biologically to produce children, and some of those children grew up and had children of their own within modern human groups.

How much Neanderthal DNA do people have?

It depends on whom you ask and how they count. Estimates for present-day people outside Africa range from about 1 to 4 percent, and published figures for Europeans cluster near 1.8 to 2.4 percent, with East Asians slightly higher at roughly 2.3 to 2.6 percent. A January 2025 study in Science, from a team including Leonardo Iasi and Manjusha Chintalapati, summarized the figure for non-Africans as about 1 to 2 percent.

A different question is how much of the whole Neanderthal genome survives across all living people. One estimate puts that near 20 percent: your genome carries only a sliver, but different people carry different slivers, and added together they cover a fifth of what Neanderthals had.

Researchers who study South Asia found similar numbers. A 2024 analysis of about 2,700 Indian genomes found 1 to 2 percent Neanderthal and Denisovan DNA combined.

What about people of African ancestry?

For a long time the standard view was that Sub-Saharan Africans carried essentially none. A 2020 study changed that picture a little, detecting 0.3 to 0.5 percent in five African populations. The likely cause is that people with Eurasian ancestry moved back into Africa in recent millennia, bringing Neanderthal DNA with them. That is the proposed explanation, not a demonstrated one.

There is also evidence of an older meeting. Some analyses suggest an earlier contact around 250,000 years ago, whose traces show up in Neanderthal genomes rather than ours.

When did the interbreeding happen?

Most of the Neanderthal DNA in people today comes from an episode that seems to have taken place between about 65,000 and 47,000 years ago, with wider estimates reaching from 86,000 to 37,000 years ago. A study by Iasi and colleagues, published in Science in December 2024, estimated that the main pulse of gene flow occurred around 47,000 years ago and lasted about 7,000 years. The team tied it to archaeological evidence that modern humans and Neanderthals overlapped in Europe and western Asia.

A companion paper in Nature, by Sümer and colleagues, studied genomes from Zlatý kůň in Czechia and from Ranis in Germany, dated to about 45,000 years ago. These people carried the same Neanderthal ancestry as everyone outside Africa today, which supports a single shared gene-flow event, but they showed no recent Neanderthal mixing of their own. They belonged to a lineage that split from other non-African groups early, and the same press material notes that they carried traits tied to their recent African origin, including dark skin, dark hair and brown eyes. Their genomes are a reminder that the story of how humans spread across Eurasia had more than one thread.

Why does the date matter? Because it pins the mixing to a window when both groups were physically in the same regions, and it fits the observation that every non-African population shares the same core Neanderthal signal. A later, separate mixing event in each region would have left different patterns, and mostly it did not.

What did Neanderthals pass on to us?

Most of what researchers have linked to Neanderthal variants involves three areas: immunity, skin and hair, and metabolism. The January 2025 Science analysis found that regions with consistently higher Neanderthal ancestry were associated with skin pigmentation, metabolism and the immune system.

Immunity is the clearest. Neanderthal variants near genes such as OAS1, STAT2 and several Toll-like receptor genes have been connected to viral defense. One estimate says about a quarter of the Neanderthal DNA in Europeans, and roughly a third in East Asians, may relate to viral immunity. The reasoning is that Neanderthals had lived in Eurasia for a long time, and their immune systems had adapted to local pathogens that newcomers lacked. Borrowing those variants may have helped. That is a hypothesis, supported by patterns of retention, not a proven story for each gene.

Keratin-related genes, which affect skin and hair, also came from Neanderthals in both Europeans and East Asians, possibly aiding adaptation to cooler, less sunny climates. A particular variant of the MC1R gene, found mainly in East Asian populations, has been weakly associated with red hair and UV sensitivity, though the link is not strong.

Is Neanderthal DNA bad for us?

Some of it is, and it has been linked to disease risk. Neanderthal-derived variants have been associated with lupus, and a 2017 study of Turkish people connected archaic genes to coeliac disease and the severity of malaria. Such associations should not be overread. A variant that raises risk for one condition may lower it for another, and the effect of any single variant is usually small compared with environment and the rest of the genome. This is a list of findings from association studies, which show correlation, not direct cause.

The interesting evidence is that many harmful variants were removed. The 2025 analysis concluded that natural selection acted quickly, within roughly 10,000 years, to purge the variants it judged detrimental. The 2024 Science study similarly found that harmful variants were lost soon after interbreeding. This is consistent with a long-standing idea: Neanderthals lived in small populations, where mildly harmful mutations pile up, and modern humans, with larger populations, selected against them.

Are there parts of the genome with no Neanderthal DNA?

Yes. Some stretches, sometimes called Neanderthal deserts, have strongly reduced Neanderthal ancestry. The effect is most pronounced on the X chromosome and in genes active in the testes. Researchers propose purifying selection against the variants, and possibly reduced fertility in hybrid males, as causes. A 2023 study attributed low Neanderthal ancestry on the X chromosome to a mix of sex-biased admixture and negative selection.

Related evidence concerns the parent of the hybrids. Modern humans carry no Neanderthal mitochondrial DNA, which suggests the matings were mostly between Neanderthal males and modern human females. A separate study reported that Neanderthal Y chromosomes were replaced by an extinct modern human Y lineage. These are inferences from patterns, so the true picture of who mated with whom could be more complicated.

What about Denisovans?

Denisovans were a sister group to Neanderthals known mostly from DNA recovered in Denisova Cave in Siberia. Neanderthals and Denisovans are more closely related to each other than either is to us. They also interbred: about 17 percent of the Denisovan genome appears to come from Neanderthals, and a 90,000-year-old individual from the cave, Denisova 11, had a Neanderthal mother and a Denisovan father.

Some living people carry Denisovan DNA too, particularly in parts of Asia and Oceania. Tibetans carry a Denisovan-derived version of the EPAS1 gene that limits hemoglobin rise at altitude, a useful adaptation. So Neanderthals were one of several archaic groups that contributed to the human gene pool.

Does having more Neanderthal DNA change who you are?

Not in any dramatic way, and be skeptical of consumer claims. Commercial ancestry reports sometimes rank customers by Neanderthal percentage, which is fine as trivia. The numbers differ by only tiny amounts between individuals, and no reputable study shows that a bit more or less shapes intelligence, character or ability.

What the science supports is narrower. Particular variants, at particular locations, have measurable effects on things like immune response or skin traits. Other claims, such as links to mood or behavior, appear in the literature but I would treat them as unsettled unless a specific study is cited.

Common questions

How much Neanderthal DNA do I have?

If your ancestry is from outside Africa, probably about 1 to 2 percent, though estimates vary by study and population. People of mostly Sub-Saharan African ancestry have far less, around 0.3 to 0.5 percent in one 2020 study.

Did Neanderthals go extinct or were they absorbed?

Both ideas appear in discussion, but the genetic evidence shows only limited mixing. Neanderthal lineages disappear from the record around 40,000 years ago, while some of their DNA survives in us.

Could Neanderthals and humans really have children together?

Yes, the genomic evidence says so. It also suggests the pairings were not entirely smooth, since some regions show strong selection against Neanderthal variants.

Is Neanderthal DNA linked to disease?

Some variants are linked to conditions such as lupus. The links are statistical and the effects on any individual are small.

Do Neanderthal genes make people less intelligent?

There is no good evidence for that. Claims along these lines are not supported by the studies discussed here.

Can a DNA test tell me my Neanderthal percentage?

Consumer tests report an estimate based on a reference set of variants. The figures are rough and differ between companies.

What to remember

Interbreeding happened, mostly between about 50,000 and 45,000 years ago, and the legacy in non-African people today is roughly 1 to 2 percent of the genome. Some inherited variants helped, mainly with immunity and skin, and many harmful ones were purged. Beyond that, be cautious about big claims on behavior or intelligence. Researchers are still learning how much each of these inherited pieces actually does.

Further reading

First-person account by the scientist who sequenced the Neanderthal genome. See it on Amazon (affiliate link)

As an Amazon Associate I earn from qualifying purchases. A commission may be earned if you buy through this link, at no extra cost to you.

Sources