Scientists have identified the oldest DNA ever discovered and, in doing so, revealed a complex ecosystem that existed two million years ago in modern Greenland, according to the results of a new study published in the journal Nature .
The double helix-shaped molecule Deoxyribonucleic acid (or DNA for short) is present in almost every cell in our human body, as well as in those of the plants and animals that inhabit our planet.
Each DNA molecule contains within it a genetic code unique to each individual and serves as a vital instruction manual for our cells that helps govern the development and functioning of our body. It is also an incredibly useful molecule for scientists looking to decode the secrets of the ancient past.
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Indeed, researchers are able to determine which species of animals or plants existed during a given window of Earth’s evolutionary history by looking for DNA fragments in well-preserved samples that , in some cases, date back hundreds of thousands of years.
Once these samples are identified, scientists can match the genetic codes found in the DNA with their closest modern counterparts, to determine what type of animal or species they belong to. In this way, humanity can build a picture of entire ecosystems that have been lost over time and gain valuable information about the evolution of life on our planet.
Unfortunately, this technique is limited by the lifespan of a DNA molecule. Once cells begin to die, enzymes get to work breaking the bonds that hold these vital molecules together. Under normal conditions in animals, this decomposition process will render DNA useless in about 521 years.
However, when the right conditions allow DNA to be stored quickly and stably, samples have been known to survive much longer.
In the new study, scientists were able to recover 41 ancient DNA samples from the mouth of a fjord located at the northernmost point of Greenland, where the landmass meets the Arctic Ocean. Each of the DNA samples extracted from the rock – known as the København Formation – was just a few millionths of a millimeter long and encased in a protective shell of clay and quartz.
By applying a combination of radiocarbon and molecular dating techniques, the international team of more than 40 scientists were able to estimate that the DNA was on average around 2 million years old. This makes them a million years older than the previous record holder of ancient DNA, which was recovered from the bone of a Siberian mammoth.
“The ancient DNA samples were found buried deep in sediments that had accumulated over 20,000 years,” comments Professor Kurt Kjær from the University of Copenhagen, who helped lead the research. “The sediment was ultimately preserved in ice or permafrost and, crucially, was undisturbed by humans for two million years.”
After painstakingly comparing the DNA with data from the 21st century, the team was able to decode the fingerprints of a thriving ancient ecosystem locked inside the samples.
When the København Formation was created around two million years ago, Greenland was a more hospitable place, with temperatures around 10 to 17 degrees Celsius warmer than they are today .
DNA evidence has revealed the presence of countless species of plants in the ancient environment, including forms of poplars and birches. Among these trees would have roamed lemmings, reindeer, hares and even giant elephantine creatures called Mastadon. There were also DNA fragments that could not be compared to any modern animal or plant.
Many samples have been waiting to be analyzed since they were first collected from the Greenland site in 2006.
“It was only when a new generation of DNA extraction and sequencing equipment was developed that we were able to locate and identify extremely small and damaged DNA fragments in sediment samples,” explained Professor Kjær. “It meant that we were finally able to map a two-million-year-old ecosystem.
The scientists behind the new study believe the relatively warm environment of ancient Greenland is comparable to temperatures we might see in the future due to global warming. Modern climate change is considered a serious threat to biodiversity globally, and the speed at which species can adapt to changing environments and warming temperatures will be key to their survival.
“The data suggests that more species can evolve and adapt to wildly variable temperatures than previously thought,” said Assistant Professor Mikkel Pedersen of the Lundbeck Foundation GeoGenetics Centre, co-first author of the new paper. “But, above all, these results show that they need time to do so.”
It is hoped that by analyzing the DNA of ancient trees and plants, scientists can unlock the secrets of their adaptation to their warm environment and potentially learn how to make today’s endangered species more resilient to climate change. .
In the future, the team hopes to discover other examples of truly ancient DNA in clay from Africa that could shed light on humanity’s earliest ancestors.
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Anthony is a freelance contributor covering science and gaming news for IGN. He has over eight years of experience covering groundbreaking developments in multiple scientific fields and has absolutely no time for your shenanigans. Follow him on Twitter @BeardConGamer
Image Credit: Beth Zaiken
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