The most ancient DNA ever discovered reveals a thriving ecosystem lost in time
Scientists have identified the most ancient DNA ever found, and in the process 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 molecule Deoxyribonucleic acid (or DNA for short) is present in almost every cell of our human bodies, as well as those of the plants and animals that inhabit our planet.
Each DNA molecule contains within it a genetic code that is unique to each individual and serves as a vital instruction manual for our cells that helps govern how our bodies develop and function. It is also an incredibly useful molecule for scientists looking to decode the secrets of the ancient past.
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That’s because researchers are able to determine what kinds of animals or plants existed during a given window in Earth’s evolutionary history by looking for fragments of DNA in well-preserved samples, which 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 to 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 gain valuable insight into the evolution of life on our planet.
Unfortunately, this technique is limited by the lifetime of a single DNA molecule. Once cells begin to die, enzymes go to work, breaking down the bonds that hold these vital molecules together. Under normal conditions in animals, this decay process will render the DNA useless after about 521 years.
However, when the right conditions allow DNA to be preserved quickly and stably, samples are 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 land meets the Arctic Ocean. Each of the DNA samples extracted from the rock – known as the København Formation – is only 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 over 40 scientists was able to estimate that the DNA has 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.
“Ancient DNA samples were found buried deep in sediment that had accumulated over 20,000 years,” comments Professor Kurt Kjær from the University of Copenhagen, who helped conduct 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 21st-century data, the team was able to decode the fingerprints of a thriving, ancient ecosystem locked inside the samples.
At the time the København Formation formed about two million years ago, Greenland was a more hospitable place, with temperatures approximately 10 – 17 degrees Celsius higher than today.
DNA evidence revealed the presence of countless types of plant life in the ancient environment, including forms of poplar and birch. Lemmings, reindeer, rabbits and even giant elephant creatures called Mastadons have roamed among these trees. There were also DNA fragments that could not be matched 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 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 the sediment samples,” Professor Kjær explained. “This meant we were finally able to map a two-million-year-old ecosystem.”
The scientists behind the new study believe that the relatively warm environment of ancient Greenland is comparable to the temperatures we may see in the future as a result of global warming. Modern day climate change is considered a serious threat to biodiversity on a global scale and the speed with which species can adapt to changing environments and warming temperatures will be key to their survival.
“The data show that more species can evolve and adapt to wildly varying temperatures than previously thought,” said Assistant Professor Mikkel Pedersen of the Lundbeck Foundation’s GeoGenetics Center, co-author of the new paper. “But most importantly, these results show that they need time to do that.”
It is hoped that by analyzing the DNA of ancient trees and plants, scientists will be able to unravel the secrets of how they adapted to hot environments and possibly learn how to make today’s endangered species more resilient to climate change.
Moving forward, the team hopes to find 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 video game news for IGN. He has over eight years of experience covering groundbreaking developments in multiple scientific fields and has absolutely no time for your antics. Follow him on Twitter @BeardConGamer
Image credit: Beth Zeiken