- BBC News World
Imagine that all the pages of a dictionary have been destroyed in a paper shredder and you need to restore the work.
Imagine that, in addition, the thousands of strips of paper from this dictionary were mixed with those from thousands of other books that were also cut up.
To this mountain of confetti, pour a cup of coffee on top.
The result: a huge sticky ball that mixes millions of letters, tiny segments of text that have become unreadable, and confuses them within itself.
Would you retool the dictionary?
This is how the Swedish scientist describes it Svante Piabo in the documentary First Nations (“First Peoples,” on the American Public Television Network, PBS) the difficulty it implied for him, or for any other person, to reconstruct Neanderthal DNA after tens of thousands of years of extinction.
The passage of time, the corrosion of the possible remains of those people before Homo sapiensinteraction with bacteria and fungi over hundreds of centuries and interaction with modern humans made it impossible to put the pieces back together.
“There are all kinds of DNA damage that can cause you to determine the wrong sequences, especially when you start with very few molecules, and there is also human DNA contamination, which is almost everywhere,” Pääbo wrote in a paper published in 1989 .
But Pääbo and his team succeeded, and thanks to it, he won the 2022 Nobel Prize in Medicine on Monday.
“Through his pioneering research, Svante Pääbo achieved something seemingly impossible: sequencing the Neanderthal genomean extinct relative of modern humans,” the Nobel committee said in announcing its decision.
The key in ancient Egypt
To understand the process that led 67-year-old Pääbo to reconstruct the Neanderthal genome, it is necessary to go back to his adolescence.
When he was 13, his mother took him on holiday to Egypt.
There he became fascinated by the ancient culture and archeology of the country, so he returned convinced that he wanted to become an Egyptologist.
When it was time to start university, Pääbo entered Uppsala University, 70 kilometers northwest of Stockholm, and began majoring in Egyptology.
After two years, however, he realized that this was not what he was aiming for in life. His career was oriented towards the study of hieroglyphic grammar and he dreamed of discovering mummies and pyramids.
“It wasn’t at all the romance and Indiana Jones type of thing I thought it would be,” Piabo told the BBC a few years ago.
For this reason, he switched to medicine and then studied for a PhD in molecular genetics, which led him to connect his interest from adolescence to his professional field.
“I started to realize that we have all these DNA cloning technologies, but no one seems to have applied them to archaeological remains, especially Egyptian mummies,” Pääbo said in a profile published by the US National Academy of Sciences.
Thus, may have its own genomic time machine.
The restlessness led him to study the DNA of mummies and a few years later to move to California to study ancient DNA at the University of California, Berkeley.
He then continued his work in Munich, Germany, where he devoted himself to mammoths and bears that live in caves.
Despite the difficulties, he not only did not give up, but in time proposed something much more ambitious: decipher Neanderthal DNA and how it differs from modern humans.
Without looking for it, he created a new discipline in science: paleogenomics.
Skeletal remains of 40,000 years
Pääbo was employed in the late 1990s by the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.
He came from work on the mitochondrial DNA of Neanderthals, and there he was offered a qualitative leap: to study the core of DNA.
“At the new institute, Pääbo and his team continuously improved methods for isolating and analyzing DNA from archaic bone remains. The research team benefited from new technical advances that made DNA sequencing very efficient,” he said in a statement. Karolinska Institute, responsible for awarding the Nobel Prize in Medicine.
The study of the Neanderthal genome took Neanderthal bone fragments from about 40,000 years ago which have preserved the DNA code in a good way.
And one factor that contributed to this was cannibalism among these hominids.
“When we analyzed the samples, we noticed that quite often we had more success with bone fragments that actually had cut marks or were intentionally broken. According to paleontologists, this suggests that these individuals were eaten,” Pääbo told him. BBC.
“If you separate the meat from these little pieces of bone and throw them in the corner of the cave where they dry out quickly, they will have less microbial activity and dry out much faster,” he added.
“We have cannibalism to thank for the success of our Neanderthal project,” he said.
Pääbo uses advanced DNA sequencing technology and has set up laboratories with high standards of cleanliness to prevent sample contamination.
He then analyzed millions of DNA fragments and used statistical techniques to isolate them from genes that are modern contaminants.
In doing so, he not only reconstructed Neanderthal DNA, but also found connections between his genome and that of modern humans – proving that Homo sapiens they had sexual relations and offspring with Neanderthals – and in turn discovered another type of hominid that lived mainly in Asia: the Denisovans.
A series of discoveries that led the meticulous Swedish researcher to receive one of the most notable international awards.
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