# 2022 Nobel Prize in Medicine: Ancient DNA: finding the extinct humans inside our genome > The 2022 Medicine prize honours Svante Pääbo for pulling readable DNA out of bones tens of thousands of years old and sequencing the genome of the Neanderthal, an extinct relative of ours. By comparing that genome with our own, he proved that early Homo sapiens and Neanderthals had children together, so almost everyone alive outside Africa still carries a small slice of Neanderthal DNA. He also discovered a completely new kind of extinct human, the Denisovans, from a single finger bone, and in the process founded the field of paleogenomics. - Laureates: Svante Pääbo (share 1, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany) - Official citation: “for his discoveries concerning the genomes of extinct hominins and human evolution” - Course page: https://nobelexplained.com/medicine/2022-ancient-dna - Last updated: 2026-06-21 ## Explained simply (ELI5) Imagine finding a book that has been left out in the rain for 40,000 years. The pages have crumbled into tiny scraps, most of the words have washed away, and someone has spilled thousands of other books on top. Reading the original story sounds impossible. That is what reading the DNA of a Neanderthal is like. Neanderthals were an extinct kind of human, and the DNA in their old bones is broken into scraps and mixed up with the DNA of bacteria and of the people handling the bone. **Svante Pääbo** spent decades inventing careful tricks to pick out the real Neanderthal scraps and piece the story back together. > **We are part Neanderthal** When Pääbo finally read the Neanderthal's DNA and compared it to ours, he found something amazing. Long ago our ancestors and Neanderthals had children together. Because of that, almost everyone alive today whose family comes from outside Africa carries a little bit of Neanderthal DNA, about 1 to 2 percent. He even discovered a brand-new kind of extinct human, the **Denisovans**, from a single tiny finger bone, just by reading the DNA hidden inside it. ## Explained for undergraduates Every cell carries DNA, a long chemical text spelling out how to build a body. The moment an organism dies, that text starts to fall apart. The molecule breaks into ever shorter fragments and slowly chemically degrades, so after thousands of years only trace amounts survive, swamped by DNA from soil bacteria and from anyone who later touches the bone. Pulling a real, readable genome out of that mess is the core challenge Pääbo solved. His first breakthrough used **mitochondrial DNA**, a small loop of DNA that each cell carries in many copies, so more of it survives. In 1997 his team read mitochondrial DNA from a Neanderthal bone from the Neander Valley in Germany. It was a glimpse, but the tiny loop holds only a sliver of the full picture, so Pääbo set out to read the entire **nuclear genome**. > **An impossible task, finished in 2010** At his new institute in Leipzig, Pääbo's team improved the methods to extract and analyse DNA from archaic bone and harnessed new high-throughput sequencing machines and population geneticists as collaborators. In 2010 they published the first draft of the Neanderthal nuclear genome, the complete genetic blueprint of an extinct human. Comparing that genome with people alive today revealed the twist. Neanderthal DNA matches present-day Europeans and Asians more closely than it matches present-day Africans. The cleanest explanation is interbreeding: as Homo sapiens left Africa they met Neanderthals already living in Eurasia and had children with them. **Traces of extinct humans in living people** (How much of each person's genome was inherited from an extinct hominin, by ancestry. The percentages mean different things per row, so read the notes.) - Non-African ancestry: Neanderthal: ~1-2% (Inherited when Homo sapiens interbred with Neanderthals in Eurasia.) - Melanesian / SE Asian: Denisovan: up to ~6% (From a separate mixing with Denisovans in eastern Eurasia.) - Sub-Saharan African ancestry: Neanderthal: ~0% (These populations stayed in Africa, away from Neanderthals.) - Neanderthal genome recovered across all of us: ~40% (Different people carry different fragments; pooled together they reconstruct much of the genome.) Then came a second shock. In 2008 a single 40,000-year-old finger bone turned up in Denisova Cave in Siberia. Its DNA matched neither Neanderthals nor any living human. Pääbo had discovered a previously unknown kind of extinct human, the **Denisovans**, identified from genetics alone, before anyone could put a face to them. ## Explained for experts The central obstacle is that DNA is not built to last. After death the double helix fragments into pieces often shorter than 50 base pairs, and cytosine bases chemically convert in ways a sequencer misreads, so the raw signal is both scarce and error-prone. After tens of thousands of years only trace amounts of genuine (endogenous) DNA remain in a bone, buried under DNA from soil bacteria and from every modern human who handled the specimen. Pääbo's career was largely a fight against this contamination: his group built dedicated clean rooms, worked out criteria to authenticate truly ancient sequences from their tell-tale damage patterns, and steadily raised the yield of usable DNA from archaic bone. > **Why mitochondrial DNA came first** Mitochondrial DNA sits outside the nucleus in hundreds of copies per cell, so it survives in greater quantity than the single nuclear copy. That is why Pääbo's 1997 Neanderthal sequence was mitochondrial. The far larger nuclear genome only became reachable once next-generation sequencing could read enormous numbers of short fragments in parallel, which is what made the 2010 draft Neanderthal genome possible. > **Reading admixture off the genome** Because Neanderthal sequences are systematically closer to non-African than to African genomes, the simplest model is gene flow from Neanderthals into the ancestors of non-Africans. Refined estimates put Neanderthal ancestry in present-day Eurasians at about 1.5 to 2.1 percent. Since different individuals carry different segments, roughly 40 percent of the whole Neanderthal genome has been recovered across living people. The data also dated the split between modern humans and the Neanderthal/Denisovan lineage to about 550,000 to 760,000 years ago, and the Neanderthal/Denisovan split to about 380,000 to 470,000 years ago. - **1997**: Pääbo's team reads mitochondrial DNA from a Neanderthal bone from the Neander Valley, the first genetic glimpse of an extinct human. - **2008**: A 40,000-year-old finger bone is unearthed in Denisova Cave, Siberia, with exceptionally well-preserved DNA. - **2010**: Pääbo publishes the first draft Neanderthal nuclear genome and, from the finger bone's DNA, announces a brand-new extinct human, the Denisovans. The Denisovans were defined entirely by their genome, a hominin known first from its DNA rather than its bones. Comparisons showed they too interbred with Homo sapiens, leaving up to about 6 percent Denisovan ancestry in people from Melanesia and parts of South East Asia. Some of this archaic DNA is not just along for the ride: the Denisovan version of the gene **EPAS1** helps survival at high altitude and is common in present-day Tibetans, and several Neanderthal variants shape how our immune system responds to infection. **What paleogenomics opened up** - A new discipline: Pääbo's methods founded paleogenomics, the reading of whole genomes from ancient remains, now a fast-moving field of its own. - A rewritten family tree: at least two extinct hominin groups, Neanderthals in western Eurasia and Denisovans in the east, coexisted with and interbred with Homo sapiens. - A refined Out of Africa model: all living humans trace back to Africa, but non-African genomes also carry small, dateable amounts of archaic DNA. - Function, not just history: archaic gene variants such as EPAS1 and several immune genes still influence the physiology of people alive today. > “Through his groundbreaking discoveries, Pääbo opened a new window to our evolutionary past.” > (Nobel Committee for Physiology or Medicine, advanced information, 2022) ## Think first **Q:** You take a DNA sample from a 40,000-year-old Neanderthal bone. When you read what is in the test tube, what is most of that DNA actually from? **A:** **Mostly not the Neanderthal.** After tens of thousands of years the original DNA has shattered into tiny fragments and almost all of it is gone. What remains is buried under DNA from bacteria that colonised the bone and from every modern human who dug it up and handled it. Pääbo's hardest problem was separating the few genuine Neanderthal fragments from this flood of contamination. **Q:** Neanderthals went extinct around 40,000 years ago. So why can a geneticist still find Neanderthal DNA inside a person living today? **A:** **Because Neanderthals did not vanish without a trace.** When Homo sapiens spread out of Africa, they met Neanderthals and had children with them. Those children passed Neanderthal DNA down the generations, so today roughly 1 to 2 percent of the genome of anyone with non-African ancestry comes from Neanderthals. A vanished kind of human still lives on inside us. ## About 40% of the Neanderthal genome is still walking around No single living person carries much Neanderthal DNA, only a percent or two. But different people carry different pieces. Add up all those scattered fragments across humanity and roughly 40 percent of the entire Neanderthal genome still survives, hidden in the DNA of people alive today. ## Key terms - **Paleogenomics**: The reading of whole genomes from ancient remains. Pääbo's methods founded the field, which lets researchers compare extinct and living organisms gene by gene. - **Hominin**: The group that includes modern humans and our close extinct relatives, such as Neanderthals and Denisovans, after the split from other apes. - **Neanderthal**: An extinct kind of human that lived across western Eurasia and died out around 40,000 years ago. Pääbo sequenced the first Neanderthal genome in 2010. - **Denisovan**: A previously unknown extinct human, discovered by Pääbo's team from DNA in a single finger bone found in Denisova Cave, Siberia. - **Introgression**: The lasting presence of one group's genes in another after interbreeding. Archaic introgression is why non-Africans carry Neanderthal DNA and Melanesians carry Denisovan DNA. - **Mitochondrial DNA**: A small loop of DNA found in many copies per cell, outside the nucleus. Because so many copies survive, it was the first ancient DNA Pääbo could read. ## Check yourself 1. After tens of thousands of years, what is the biggest problem with the DNA left in an ancient bone? - It is frozen too solid to read - **It has broken into tiny fragments and is swamped by bacterial and modern human DNA** (correct) - It changes into a completely different molecule - There is far too much of it to handle - Why: Over time DNA degrades into short fragments and only trace amounts of the original survive, drowned out by contamination from bacteria and from the people handling the bone. **Separating real ancient DNA from that contamination** was Pääbo's central challenge. 2. Roughly how much of the genome of a person with non-African ancestry was inherited from Neanderthals? - **About 1 to 2 percent** (correct) - About half - About 25 percent - None at all - Why: Comparing genomes showed that people of European or Asian descent carry about **1 to 2 percent Neanderthal DNA**, a direct fingerprint of interbreeding as Homo sapiens spread out of Africa. 3. How were the Denisovans, a previously unknown kind of extinct human, first discovered? - From a complete skeleton - From their cave paintings - **From DNA in a single finger bone** (correct) - From fossil footprints - Why: In 2008 a single 40,000-year-old finger bone from Denisova Cave yielded well-preserved DNA that matched neither Neanderthals nor living humans. The Denisovans were **identified from genetics alone**. ## The laureates ### Svante Pääbo Born in Sweden in 1955, Pääbo trained as a molecular biologist and learned to coax DNA out of old tissue as a postdoc with the evolutionary biologist Allan Wilson at Berkeley. In 1997 he became founding director of the Max Planck Institute for Evolutionary Anthropology in Leipzig, where over two decades he turned the recovery of DNA from ancient bone from a near-impossible trick into a rigorous science and sequenced the first Neanderthal genome. ## Sources - [Press release: The Nobel Prize in Physiology or Medicine 2022 (NobelPrize.org)](https://www.nobelprize.org/prizes/medicine/2022/press-release/) - [The Nobel Prize in Physiology or Medicine 2022, advanced information (NobelPrize.org)](https://www.nobelprize.org/prizes/medicine/2022/advanced-information/) - [Svante Pääbo (Wikipedia)](https://en.wikipedia.org/wiki/Svante_P%C3%A4%C3%A4bo) --- From Nobel Explained (https://nobelexplained.com), a free, independent course on every Nobel Prize since 2020. Not affiliated with the Nobel Foundation. Facts are pinned from the official Nobel Prize API.