The Nobel Assembly has announced that this year’s Nobel Prize in Physiology or Medicine has been awarded to Swedish researcher Svante Pääbo for his pioneering work in the genetics of prehistoric humans.
Pääbo, 67, is credited with founding the science of paleogenomics by developing methods for collecting and assembling DNA from the bones of ancient humans. His breakthrough helped lead to the now widely accepted theory that modern humans—homo sapiens—and ancient humans, such as Neanderthals, interbred. He also helped advance modern genetics techniques.
Pääbo’s career has run parallel with the development of modern genetics, called genomics, which has made it possible to understand DNA in ever greater detail. The first genome sequences—detailed maps of genes—were completed in the 1990s, and in 2003 scientists sequenced 92% of the human genome. As a post-doctoral researcher in evolutionary genetics in the late 1980s, Pääbo wanted to apply genomics to the old bones of ancient humans, which, so far, had only been studied through anthropology.
Applying genomics to these old bones posed a serious technical difficulty. Over time DNA degrades into fragments, making it difficult to gather enough genetic information to be relevant. Pääbo first turned to mitochondrial DNA—DNA from energy-producing organelles in cells—which is commonly used in population genetics. Though it provides less genetic information than nuclear DNA—the complete DNA found in the nucleus of the cell—he found that mitochondrial DNA was more stable and, since thousands of copies are present in each cell, using it increased the chances of finding a complete copy of the mitochondrial DNA. This provided the first glimpse into archaic genes.
As genomics and sequencing techniques advanced, Pääbo was able to apply sequencing techniques to the fragments of nuclear DNA still found in ancient human bones. Working with previously-found Neanderthal bones such as an exceptionally well-preserved one from Croatia, he slowly stitched the Neanderthal genome back together fragment by fragment.
In 2010, he published what had, two decades before, seemed impossible—a sequence of the Neanderthal genome.
According to other scientists, Pääbo’s achievement is monumental not only for anthropology and physiology but also for genomics techniques.
“That he was able to get the complete genome sequence of a Neanderthal was viewed, even up until he did it, as an absolutely impossible feat,” Leslie Vosshall, a neuroscientist at the Rockefeller University in New York City, who is the vice president and chief scientific officer at the Howard Hughes Medical Institute told ScienceNews. “On a technical basis, the prize is also richly deserved.”
His research has enlightened the relationships between modern and ancient humans.
His sequencing of a 40,000-year-old fragment from an unusually well-preserved finger bone discovered in the Denisova cave in the southern part of Siberia in 2008 revealed another distinct human gene sequence. The ancient human was aptly named Denisova.
The ability to make sequences of archaic genomes allowed also for seeing how genes had flowed between different human populations. Archaeology and palaeontology had already shown that Neanderthals and modern humans coexisted for a millennium. Neanderthals are thought to have dominated Eurasia before Homo Sapiens, who are believed to have originated in Africa before migrating later to Europe and Asia. Pääbo found genetic evidence that where they coexisted, they also mated, as comparative analyses showed that DNA sequences from Neanderthals had more in common with sequences from contemporary humans from Europe or Asia than contemporary humans from Africa.
“This means that Neanderthals and Homo sapiens interbred during their millennia of coexistence. In modern-day humans with European or Asian descent, approximately 1-4% of the genome originates from the Neanderthals,” the Nobel Assembly explained.
Pääbo’s research has also shown genetic links between archaic and modern humans regarding specific characteristics found in some modern humans but not others.
“One such example is the Denisovan version of the gene EPAS1, which confers an advantage for survival at high altitude and is common among present-day Tibetans,” the Nobel Assembly stated. “Other examples are Neanderthal genes that affect our immune response to different types of infections.”
In humanity’s constant search to understand itself, Pääbo’s research confirms the unique and common humanity of man at all stages of evolutionary development.