Scientists have identified the most ancient DNA ever discovered, and in the process revealed a complex ecosystem that existed two million years ago in modern day Greenland, according to the results of a new study published in the journal Nature.
The double helix-shaped molicule Deoxyribonucleic acid (or DNA for short) is present in almost every cell of our human bodies, and those of the plants and animals that inhabit our planet.
Every 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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This is because researchers are able to determine what species of animal or plant existed during a given window in Earth’s evolutionary history by looking for scraps 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 day counterparts, in order 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 insights into the evolution of life on our planet.
Unfortunately, this technique is limited by the lifespan of a DNA molecule. Once cells start to die, enzymes set to work breaking down the bonds that hold these vital molecules together. Under normal conditions in animals, this decaying process will render DNA useless in some 521 years.
However, when the right conditions allow DNA to be preserved 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 most northern point of Greenland, where the landmass meets the Arctic Ocean. Each of the DNA samples extracted from the rock — known as the København Formation — were just a few millionths of a millimetre in length, and were 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 were able to estimate that the DNA was on average around 2 million years old. 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 built-up over 20,000 years,” comments professor Kurt Kjær of the University of Copenhagen, who helped lead the research. “The sediment was eventually preserved in ice or permafrost and, crucially, not disturbed by humans for two million years.”
After painstakingly comparing the DNA with data from the 21st Century, the team were able to decode the fingerprints of a thriving, ancient ecosystem locked away inside the samples.
At the time the København Formation was created some two million years ago, Greenland was a more hospitable place, with temperatures roughly 10 – 17 degrees Celsius warmer than they are today.
The DNA evidence revealed the presence of countless species of plant life in the ancient environment, including forms of poplar and birch trees. Amongst these trees would have roamed lemmings, reindeer, hares, and even giant elephantine creatures called Mastadon. There were also DNA fragments that couldn’t be matched with any modern day animal or plant.
Many of the samples have been awaiting analysis since they were first gathered from the Greenland site back in 2006.
“It wasn’t until a new generation of DNA extraction and sequencing equipment was developed that we’ve been able to locate and identify extremely small and damaged fragments of DNA in the sediment samples,” explained professor Kjær. “It meant we were finally able to map a two-million-year-old ecosystem.”
The scientists behind the new study believe that ancient Greenland’s relatively warm environment is comparable to the temperatures that we could see in the future as a result of global warming. Modern day climate change is considered to be a serious threat to biodiversity on a global scale, and the rate at which species can adapt to the changing environments and warming temperatures will be key to their survival.
“The data suggests that more species can evolve and adapt to wildly varying temperatures than previously thought,” said Assistant Professor Mikkel Pedersen of the Lundbeck Foundation GeoGenetics Centre, co-first author of the new paper. “But, crucially, these results show they need time to do this.”
It is hoped that by analysing the DNA of ancient trees and plants, the scientists will be able to unravel the secrets as to how they adapted to their hot environment, and potentially learn how to make endangered species in the present day more resistant to climate change.
Moving forward the team hope 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 video gaming news for IGN. He has over eight years experience of covering breaking developments in multiple scientific fields and absolutely no time for your shenanigans. Follow him on Twitter @BeardConGamer
Image Credit: Beth Zaiken