This year’s Nobel Prize in Physiology or Medicine goes to Svante Pääbo. One of the most important scientific achievements of him was the decoding of the Neanderthal genome. “His work has revolutionized our understanding of the evolutionary history of modern humans,” said Martin Stratmann, president of the Max Planck Gesellschaft. For example, Svante Pääbo has shown that Neanderthals and other extinct hominids have made a significant contribution to the lineage of modern humans.
Svante Pääbo studied Egyptology and Medicine at Uppsala University. As a graduate student – he earned his PhD in immunology – he also proved that DNA can survive in ancient Egyptian mummies, earning professional fame as a pioneer in the new field of paleogenetics. Paleogeneticists study the genomes of ancient organisms and use them to draw conclusions about the course of evolution.
After his doctorate, Pääbo worked in the team of evolutionary biologist Allan Wilson on University of California in Berkeley. Since 1990 he has been running his own laboratory at the Ludwig-Maximilians-University of Munich. In 1997 Pääbo became one of the five directors of the newly founded company Max Planck Institute for Evolutionary Anthropology in Leipzig, where it is still active today.
As early as the mid-1990s, Pääbo and his team were able to decode a relatively short portion of a Neanderthal’s mitochondrial DNA. Mitochondria are tiny power plants in cells that supply them with energy and have their own DNA. This Neanderthal DNA differed significantly from the genome of modern humans. This proved that Neanderthals are not the direct ancestors of modern humans.
As DNA sequencing methods became much more efficient in the early 2000s, Pääbo began sequencing the entire Neanderthal genome present in the cell nucleus.
A giant puzzle
The difficulty here: After thousands of years, Neanderthal bones in soil are so heavily colonized by bacteria and fungi that up to 99.9 percent of the DNA found in them is from microbes. Furthermore, the small amounts of remaining Neanderthal DNA are only available in short fragments that need to be put together like a giant puzzle. Many scientists believed that this task was unsolvable.
However, the Pääbo team came up with new solutions. The researchers worked in “clean room conditions” comparable to those of the chip industry. In this way, they were able to prevent them from accidentally introducing their own DNA into the experiments. In addition, they developed more efficient extraction methods that improved the yield of Neanderthal DNA. Complex computer programs that compared the DNA fragments of ancient bones with the reference genomes of chimpanzees and humans helped to reconstruct the Neanderthal genome.
In 2010, Svante Pääbo and his team managed to reconstruct an early version of the Neanderthal genome from bones that are tens of thousands of years old. Comparisons of the Neanderthal genome with the genomes of modern humans revealed that when modern humans left Africa and arrived in Europe and Asia, modern humans and Neanderthals had mated about 50,000 years ago.
Even today, about two percent of Neanderthal DNA is found in the genome of today’s non-African people. This genetic contribution influenced human evolution: for example, it strengthened the immune system of modern humans, but still contributes to susceptibility to various diseases today.
“Neanderthals are the closest relatives of modern humans,” said Svante Pääbo. “Comparisons of their genomes with those of modern humans and those of great apes allow us to determine when genetic changes occurred in our ancestors.” In the future, it could also explain why modern humans eventually developed a complex culture and technology that allowed them to colonize almost the entire world. However, this required a more complete understanding of the Neanderthal genome than the team achieved in 2010.
Get to the bottom of human origins
In 2014 the team was successful Max Planck Institute for Evolutionary Anthropologyto almost completely decode the Neanderthal genome. This made a comparison with the genomes of modern humans possible. “We found about 30,000 locations where the genomes of nearly all modern humans differ from those of Neanderthals and great apes,” says Pääbo. “They respond to what makes anatomically modern humans ‘modern’ in a genetic sense as well.” Some of these genetic changes may be the key to understanding what differentiates the cognitive abilities of modern humans from those of now extinct hominids.
In view of this, Svante Pääbo’s team had already caused a sensation in 2012: they decoded the genome from a small bone they had found in the Denisova cave in the Altai Mountains of western Siberia. Loosely related to Neanderthals, enigmatic primeval humans contributed up to five percent of the genome of present-day Papua New Guinea inhabitants, Australian aborigines, and other groups in Oceania.
Researchers are currently working on new methods to reconstruct DNA fragments that are even more decomposed and present in even smaller quantities. The goal is to enable the study of even older DNA, as well as genetic material from parts of the world where DNA survival is even rarer due to hot, humid climates.
Like father Like Son
Svante Pääbo’s father, Sune Bergström, was awarded the highest scientific recognition: the biochemist received the Nobel Prize in Physiology and Medicine along with Bengt Ingemar Samuelsson and Sir John Robert Vane in 1982 for their groundbreaking work on prostaglandins and on closely related biologically active substances.
The Nobel Prize in Physiology or Medicine is one of the five original prizes donated by the Swedish inventor Alfred Nobel. It has been published every year since 1901 by the Swedes Karolinska Institute awarded and is endowed with eight million Swedish kronor (approximately 775,000 euros). On 10 December, the anniversary of Alfred Nobel’s death, the highest scientific award will be awarded by the King of Sweden in Stockholm. (SJ / BA / mpg)
