Neanderthal and Denisovan DNA Discoveries Win 2022 Nobel Prize
The 2022 Nobel Prize for Physiology or Medicine has been awarded to a Swedish researcher who revealed the sequence of the Neanderthal genome through decades of painstaking DNA detective work. Winner Svante Pääbo, director of the Max Planck Institute for Evolutionary Anthropology, was also laureated for his discovery of a related ancient human, the Denisova.
The accolade includes a 10m Swedish kronor (£800,000) prize.
The genome of Neanderthals: revealed
The advance of DNA sequencing techniques has led to numerous breakthroughs throughout the 21st century. But Pääbo’s work in teasing out the sequences of the Neanderthal genome came with an additional complexity: these ancient genomes typically become broken down over time, leaving researchers with just fragments of DNA to sift through. Further, these chunks are often found as a complex mix, with genomic information from bacteria, and even modern-day humans muddying the picture.
Who were the Neanderthals? Neanderthals – the extinct species of archaic humans known as Homo neanderthalensis – are our closest evolutionary relatives. The first recognized Neanderthal fossils were discovered in 1856, in the Neander Valley in Germany. Both Neanderthals and early humans – Homo sapiens – inhabited the same areas in Europe and western Asia for approximately 2,600 to 5,400 years, although the last traces of Neanderthals disappeared around 40,000 years ago. They had a strong, stocky build with short arms and legs, and distinctive faces characterized by large brow bones. They were intelligent and able to communicate, enabling them to be both proficient toolmakers and hunters.
Beginning during a stint as a professor at the University of Munich, Pääbo’s first efforts towards sequencing ancient DNA targeted the Neanderthal mitochondrial genome. There are far more copies of these smaller genomes present in cells, and Pääbo found success using a hunk of 40,000-year-old bone.
But it was to be his subsequent work in patching together the nuclear Neanderthal genome that would become his magnum opus. After decades of work, Pääbo and colleagues unveiled the first Neanderthal genome in 2010. In addition to providing valuable information on one of humanity’s closest relatives, this effort also enabled subsequent research toward identifying exactly what makes us different from these other ancient humans. Pääbo also led some of these efforts, showing that modern-day Asians and Europeans had a closer genetic link to ancient Neanderthals than modern-day Africans, a finding that suggests interbreeding between humans and their hominin relatives in the period after Homo sapiens first migrated from Africa, 100,000–200,000 years ago.
A whole new ancient human
Pääbo’s efforts towards demystifying Neanderthals would be enough to occupy any researcher’s career. But Pääbo was at the forefront of a second influential research project that would identify another ancient human, this time one previously unknown to science.
Who were the Denisovans?
The Denisovans are an extinct archaic human subspecies. Discovered only a decade ago, we know very little about the Denisovans. Their DNA shows that Denisovans last shared a common ancestor with both Neanderthals and our own species approximately 765,000 years ago. However, most studies refer to Denisovans as a “population”, as we do not yet know enough about them to classify them as a distinct species owing to the lack of fossil material.
Pääbo and his team sequenced a 40,000-year-old finger bone found in a cave in a region of southern Siberia. The bone was found to be neither from an ancient Homo sapiens nor Homo neanderthalensis; Pääbo had identified the remains of another hominin group, which would come to be dubbed the Denisova, after the cave in which they were found. Denisovan DNA has now been found in contemporary human genomes around the world. The Filipino Ayta Magbukon ethnic group was found to have the highest proportion of Denisovan DNA recorded to date in 2021.
Ultimately, write the Nobel Prize committee in their initial laureation, Pääbo’s work has spawned an entirely new field, paleogenomics. His work in deciphering the DNA of ancient humans and using that code to inform our understanding of our modern physiology is an effort that will be carried forward by generations of scientists.
"By revealing genetic differences that distinguish all living humans from extinct hominins, his discoveries provide the basis for exploring what makes us uniquely human", the Nobel committee concluded.