Scientists have identified the oldest DNA ever discovered and, in the process, revealed a complex ecosystem that existed two million years ago in present-day Greenland, according to the results of a new study published in the journal. Nature.
The double-helical molecule of deoxyribonucleic acid (or DNA for short) is present in almost every cell in our human body and in those of the plants and animals that inhabit our planet.
Each DNA molecule contains a genetic code that is unique to each individual and serves as a vital instruction manual for our cells that helps control how our bodies develop and function. It is also an incredibly useful molecule for scientists looking to unlock the secrets of the ancient past.
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That’s because researchers can determine which animal or plant species existed during a given window in Earth’s evolutionary history by looking for snippets of DNA in well-preserved samples that, in some cases, date back hundreds of thousands of years.
Once these samples have been 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 to the relentless passage of time and obtain valuable information about the evolution of life on our planet.
Unfortunately, this technique is limited by the lifetime of a DNA molecule. Once cells begin to die, enzymes go to work breaking the bonds that hold these vital molecules together. Under normal conditions in animals, this decay process will render DNA useless in about 521 years.
However, when the right conditions allow DNA to be quickly and stably preserved, samples have been known to survive much longer.
In the new study, scientists were able to recover 41 samples of ancient DNA 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 only a few millionths of a millimeter in length and encased in a protective layer of clay and quartz.
By applying a combination of radiocarbon and molecular dating techniques, the international team of more than 40 scientists was able to estimate that the DNA had an average age of around 2 million years. This makes them 1 million years older than the previous record holder for ancient DNA, which was recovered from the bone of a Siberian mammoth.
“The ancient DNA samples were found buried deep in sediment that had accumulated over 20,000 years.” comments Professor Kurt Kjaer from the University of Copenhagen, who helped lead the research. “The sediment was eventually preserved in ice or permafrost and, importantly, undisturbed by humans for two million years.”
After painstakingly comparing the DNA to 21st century data, the team was able to decode the fingerprints of a thriving ancient ecosystem locked within the samples.
At the time the København Formation was created some two million years ago, Greenland was a more hospitable place, with temperatures 10-17 degrees Celsius warmer than today.
DNA evidence revealed the presence of countless species of plant life in the ancient environment, including forms of poplar and birch. Among these trees would have roamed lemmings, reindeer, hares, and even gigantic elephantine creatures called Mastadon. There were also bits of DNA that couldn’t be compared to any modern animal or plant.
Many of the samples have been awaiting analysis since they were first collected from the Greenland site in 2006.
“It was not until 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. capable of mapping an ecosystem two million years old.
The scientists behind the new study believe that the relatively warm environment of ancient Greenland is comparable to temperatures we might see in the future as a result of global warming. modern day climate change It is considered a serious threat to biodiversity on a global scale, and the speed at which species can adapt to changing environments and rising temperatures will be key to their survival.
“The data suggests that more species may evolve and adapt to widely varying temperatures than previously thought,” said Assistant Professor Mikkel Pedersen of the Lundbeck Foundation Center for GeoGenetics, co-author of the new paper. “But crucially, these results show that they take time to do this.”
It is hoped that by analyzing the DNA of ancient trees and plants, scientists can unlock the secrets of how they adapted to their hot environment, and potentially learn how to make today’s endangered species more resilient to climate change. . .
In the future, the team hopes to discover more 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 the latest developments in multiple scientific fields and has no time for his antics. Follow him on Twitter @BeardConGamer
Image Credit: Beth Zaiken
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