Human Evolution

Do Humans Have Neanderthal DNA?

Neanderthals vanished from the fossil record around 40,000 years ago. They did not, however, vanish from us. A portion of every non-African person alive today is, in the most literal genetic sense, Neanderthal.

The short answer

Yes. Non-African humans carry approximately 1–4% Neanderthal DNA, the result of interbreeding that occurred between 40,000 and 60,000 years ago as Homo sapiens moved into Europe and Asia. The hybridization happened multiple times, produced fertile offspring, and left permanent marks on human biology including immune genes that may still be protecting us today.

Editorial illustration contrasting Homo sapiens and Neanderthal skulls with a DNA double helix

Neanderthal DNA in non-Africans

Approximately 1–4% of the genome confirmed by whole-genome sequencing

African populations

Carry little to no Neanderthal DNA the interbreeding happened after Homo sapiens left Africa

Denisovans too

Some Asian and Australasian populations also carry DNA from a second archaic human group, the Denisovans

Still active

Inherited Neanderthal variants influence immune response, skin and hair characteristics, and depression risk

When it happened

Mostly 40,000–60,000 years ago, over multiple encounters spanning thousands of years

Visual answer

Where Neanderthal DNA ended up and what happened to it

The journey of Neanderthal genetic variants into the modern human genome, and what selection has done to them since

1

The interbreeding event

~50,000–60,000 years ago in the Middle East Homo sapiens meets Neanderthal populations already resident in Eurasia

2

Fertile offspring

Hybrids were viable and fertile Neanderthal DNA entered the human gene pool permanently

3

Spreading with migration

As Homo sapiens spread across Eurasia, they carried their Neanderthal inheritance with them

4

Selection over 50,000 years

Harmful Neanderthal variants were gradually selected out; useful ones (immune, skin) persisted leaving the 1–4% signature we see today

The verdict

Verdict

Yes non-African humans are part Neanderthal, and the evidence is definitive

Confidence99%

The discovery was made in 2010 by Svante Pääbo and colleagues at the Max Planck Institute, who sequenced the Neanderthal genome from bone fragments and compared it to modern human genomes. They found that non-African humans share more DNA with Neanderthals than African humans do the signature of interbreeding after the Out of Africa migration. This has since been replicated and refined extensively. We now know hybridization occurred multiple times, in multiple locations, and that the resulting offspring were fertile. Pääbo received the Nobel Prize in Physiology or Medicine in 2022 for this work.

Useful analogy

Think of the human genome as a text that has been copied, hand to hand, for 300,000 years. Most of the text is ours. But scattered through the chapters written in Europe and Asia are sentences sometimes whole paragraphs that were borrowed from a different manuscript. Some of those borrowed passages are doing something useful. Some may be causing problems. Most we don't yet fully understand.

The catch

While non-African humans are ~1–4% Neanderthal, the Neanderthal variants aren't randomly distributed they cluster in certain functional regions of the genome, particularly immune genes, and are notably absent from others, particularly regions involved in brain development and fertility. This suggests that most of the rest of the inherited Neanderthal DNA was gradually selected out over tens of thousands of years because it was slightly harmful in a modern human context.

How we found out

How scientists extracted a genome from a 40,000-year-old bone

Neanderthal DNA was recovered from bone fragments found in Croatian caves. Ancient DNA is not pristine it's broken into tiny fragments, chemically degraded, and thoroughly contaminated with bacterial DNA and the DNA of every human who has ever handled the specimen. Pääbo's team developed techniques to chemically distinguish ancient DNA from modern contamination, then laboriously assembled the fragments into a genome like a billion-piece jigsaw where most of the pieces are damaged and some belong to completely different puzzles.

The resulting Neanderthal genome was compared to modern human genomes from five people on different continents. The finding was stark: the European and Asian genomes were more similar to the Neanderthal genome than the African genomes were. The only explanation that fits is interbreeding at some point after Homo sapiens left Africa but before they spread across Eurasia, they encountered and interbred with Neanderthals.

Subsequent work has refined the picture considerably. We now know the mixing happened in the Middle East around 50,000–60,000 years ago, as well as possibly in Europe later. It happened multiple times. And it wasn't just Neanderthals populations in East Asia and the Pacific carry additional DNA from a separate archaic group called the Denisovans, known from a single finger bone found in a Siberian cave.

What Neanderthal DNA does

What inherited Neanderthal variants actually do in modern humans

Immune genes (HLA)

Some Neanderthal immune variants are more common today than chance would predict suggesting they provided protection against Eurasian pathogens that Homo sapiens hadn't encountered before.

Skin and hair

Certain Neanderthal variants influence skin pigmentation and hair texture. Neanderthals had lived in Europe for 300,000 years; inheriting some of their adaptations to lower UV environments made sense.

Blood clotting

Some inherited variants increase blood clotting tendency potentially useful in wounds, but associated with higher risk of stroke and miscarriage in modern contexts.

Depression and mood

A cluster of Neanderthal-derived variants on chromosome 12 has been associated with increased risk of depression. How and why is not well understood.

Brain and fertility

Neanderthal variants are notably absent from genes involved in brain development and sperm production suggesting these were selected out because they were harmful in a modern human background.

Were they really different species?

If Neanderthals were a separate species, how could they interbreed with us?

What people think

"Neanderthals and Homo sapiens were completely separate species they couldn't possibly have interbred"

Species are defined, in part, by reproductive isolation. If Neanderthals were a separate species, the thinking goes, they couldn't have produced fertile offspring with Homo sapiens.

What actually happens

They were separate enough to be called a different species and similar enough to produce fertile children

This is precisely what makes the Neanderthal story so philosophically interesting. Neanderthals and Homo sapiens diverged roughly 600,000 years ago far more recently than humans and chimpanzees (6 million years), and close enough that chromosomal compatibility was maintained. The fertile hybrids are the evidence that the species boundary, at that divergence distance, was real but permeable. Some biologists argue that Neanderthals shouldn't be classified as a separate species at all that they and modern humans were subspecies of Homo sapiens. The genome data, which keeps revealing more mixing, not less, tends to support the fuzzier view.

Quick answers

Common questions

Quick answers

Common questions

Does having Neanderthal DNA make you less or more human?

Neither it makes you more interesting. The question assumes a clean boundary between 'human' and 'not human' that the genetics simply doesn't support. Homo sapiens and Neanderthals were different enough to diverge into separate populations over hundreds of thousands of years, and similar enough to find each other attractive and produce children who lived and reproduced. The categories are real. They are also, evidently, porous. Most things in biology are.

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