Oldest DNA on record - 2 million years - reveals Greenland's lost world
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[December 08, 2022]
By Will Dunham
WASHINGTON (Reuters) - Scientists have identified DNA from animals,
plants and microbes dating to about 2 million years ago - the oldest on
record by far - from sediment at Greenland's northernmost point dug up
around the mouth of an Arctic Ocean fjord, revealing an amazing lost
world at this remote frontier.
Researchers said on Wednesday fragments of DNA were detected for a
panoply of animals including mastodons, reindeer, hares, lemmings and
geese as well as plants including poplar, birch and thuja trees and
microorganisms including bacteria and fungi. DNA is the self-replicating
material carrying genetic information in living organisms - sort of a
blueprint of life.
The mastodon was an elephant relative that roamed North and Central
America until its extinction alongside many other large Ice Age mammals
roughly 10,000 years ago. The discovery shows that it had a wider range
than previously known.
"The mastodon was a great surprise. It's never been found on Greenland
before. However, the greatest surprise was this unique ecosystem of
Arctic and temperate species mixed together with no modern analog," said
Eske Willerslev, director of the Lundbeck Foundation GeoGenetics Centre
and leader of the study published in the journal Nature.
"I don't think anyone would have predicted Greenland holding such a
diversity of plants and animals 2 million years ago at a time when the
climate was very similar to what we expect to witness in a few years
because of global warming," added Willerslev, who is affiliated with the
University of Cambridge and University of Copenhagen.
Though ancient DNA is highly perishable, the study showed that under the
right conditions - in this case permafrost - it can survive longer than
previously believed possible. Willerslev said he now would not be
surprised to find DNA from at least 4 million years ago.
The researchers extracted and sequenced DNA from 41 organic-rich
sediment samples obtained from five sites on the Peary Land peninsula
jutting into the Arctic Ocean. Microscopic fragments of DNA were
extracted from clay and quartz in the sediment. They identified more
than 100 types of animals and plants.
The samples were first dug up in 2006, but earlier DNA detection efforts
failed. Methods used to extract ancient DNA have since improved,
eventually allowing a breakthrough.
"We think it's because the DNA bound itself to mineral particles that
enabled its survival beyond what was thought possible. The bond reduces
the rate of spontaneous chemical degradation," Willerslev said.
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A close-up view shows of organic
material in the coastal deposits at the northern tip of Greenland
that yielded DNA dating from two million years ago in this undated
photograph obtained by Reuters on December 6, 2022. Kurt Kjaer/Handout
via REUTERS
Willerslev said the fragmentary DNA cannot be used to resurrect
extinct species - as in the "Jurassic Park" books and films - but
could reveal secrets of how plants can become more resistant to a
warming climate.
"You cannot use them for cloning," Willerslev said of the DNA
remnants, "but you may use it to genetically modify living organisms
such as plants to become more adapted to a warmer climate."
The oldest previous DNA on record was extracted from the molar of a
mammoth, another elephant relative, in northeastern Siberia dating
to up to 1.2 million years ago, also preserved in permafrost
conditions. By way of comparison, our species, Homo sapiens, arose
roughly 300,000 years ago.
Most knowledge about prehistoric organisms comes from studying
fossils, but there is a limit to what these can reveal, particularly
relating to genetic relationships and traits. That is where ancient
DNA proves invaluable.
Most of modern Greenland is covered by a thick ice sheet, with
ice-free areas along the coastline. The region in the study is
considered a polar desert. But 2 million years ago Greenland's
average temperatures were 20 to 30 degrees Fahrenheit (11 to 17
degrees Celsius) higher, according to study first author Kurt Kjaer
of the University of Copenhagen.
The presence of marine species including horseshoe crab and green
algae, also among the DNA detected, illustrated that warmer climate,
the researchers said.
The DNA has revealed this ancient ecosystem in detail, with an open
boreal forest featuring trees, shrubs and smaller plants and teeming
with animals. It did not identify which large predators were present
but these may have included wolves, bears and saber-toothed cats,
according to study co-author Mikkel Pedersen of the University of
Copenhagen.
Study co-author Nicolaj Larsen of the University of Copenhagen said
the researchers are targeting sites in northern Canada for
even-older DNA.
"I think you may find such long-term survival of DNA in many places
in the world," Willerslev said. "It's simply going out there and
trying."
(Reporting by Will Dunham in Washington, Editing by Rosalba O'Brien)
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