STOCKHOLM, Sweden — Swedish paleogeneticist
Svante Paabo, who sequenced the genome of the
Neanderthal and discovered the
previously unknown hominin Denisova, on Monday won the Nobel Medicine Prize.
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Paabo’s research gave rise to an entirely new
scientific discipline called paleogenomics, and has “generated new
understanding of our evolutionary history”, the Nobel committee said.
“By revealing genetic differences that distinguish
all living humans from extinct hominins, his discoveries provide the basis for
exploring what makes us uniquely human,” it said in a statement.
Paabo — the founder and director of the department
of genetics at the Max Planck Institute for
Evolutionary Anthropology in
Leipzig — found that gene transfer had occurred from these now extinct hominins
to Homo sapiens following the migration out of Africa around 70,000 years ago.
“This ancient flow of genes to present-day humans
has physiological relevance today, for example affecting how our immune system
reacts to infections,” the jury said.
One such example
is that COVID-19 patients with a snippet of Neanderthal DNA run a higher risk
of severe complications from the disease, Paabo found in a 2020 study.
The secretary of the Nobel Medicine Prize committee,
Thomas Perlmann, told reporters Paabo was “overwhelmed” and “speechless” on
Monday when he called him in Leipzig, Germany, to share the good news.
Paabo, 67, takes home the award sum of 10 million
Swedish kronor ($901,500).
He is one of the
rare Nobel science laureates to win the prize alone. Major scientific
discoveries are usually awarded to two or three people to reflect large team
collaborations.
The last single medicine laureate was Yoshinori
Ohsumi of Japan in 2016.
Paabo is the son of Sune Bergstrom, a Swede who won
the 1982 Nobel Medicine Prize for discovering prostaglandins — biochemical
compounds that influence blood pressure, body temperature, allergic reactions,
and other physiological phenomena.
Achieved ‘the
seemingly impossible’
Homo sapiens are known to
have first appeared in Africa around 300,000 years ago.
Our closest known relatives, Neanderthals, developed
outside Africa and populated Europe and Western Asia from around 400,000 to
30,000 years ago, when they became extinct.
A bone fragment of “Denisova 11”, evidence of interbreeding of a Neanderthal and a Denisovan, found in 2012 by Russian archaeologists at Denisova Cave in the Altai Mountains of Siberia. (File photo: University of Oxford/Max Planck Institute/AFP)
That means that about 70,000 years ago, groups of
Homo sapiens and Neanderthals coexisted in large parts of Eurasia for tens of
thousands of years.
In order to study the relationship between
present-day humans and extinct Neanderthals, DNA needed to be sequenced from
archaic specimens with only trace amounts of DNA left after thousands of years.
In 1990, Paabo managed to sequence a bit of
mitochondrial DNA from a 40,000-year-old piece of bone.
“For the first time, we had access to a sequence
from an extinct relative”, the Nobel jury said.
Comparisons with contemporary humans and chimpanzees
showed that Neanderthals were genetically distinct.
Paabo then “accomplished the seemingly impossible”,
the Nobel committee said, when he published the first Neanderthal genome
sequence in 2010.
It showed that the most recent common ancestor of
Neanderthals and Homo sapiens lived around 800,000 years ago.
Paabo and his team were able to show that DNA
sequences from Neanderthals were more similar to those from contemporary humans
originating from
Europe or Asia than those from Africa.
“This means that Neanderthals and Homo sapiens
interbred during their millennia of coexistence,” the Nobel jury said.
In modern day humans with European or Asian descent,
around one to four percent of the genome originates from Neanderthals.
New addition to family tree
In 2008, Paabo and his team
went on to sequence a 40,000-year-old bone fragment found in the Denisova cave
in southern Siberia.
It contained exceptionally well-preserved DNA.
“The results caused a sensation — the DNA sequence
was unique when compared to all known sequences from Neanderthals and
present-day humans.”
Paabo had discovered a previously unknown hominin,
which was given the name Denisova.
Comparisons showed the gene flow had also occurred
between Denisova and Homo sapiens.
As a result of Paabo’s research, we now know that when Homo
sapiens migrated out of Africa, at least two extinct hominin populations
inhabited Eurasia — Neanderthals lived in western Eurasia, whereas Denisovans
populated the eastern parts of the continent.
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