Two-million-year-old DNA has been identified for the first time, opening a new “game-changing” chapter in evolutionary history.
Microscopic fragments of environmental DNA have been found in Ice Age sediments in northern Greenland. Using state-of-the-art technology, the researchers found the fragments were a million years older than the previous record of DNA taken from a Siberian mammoth bone.
Ancient DNA has been used to map a two-million-year-old ecosystem that has withstood extreme climate change. The researchers hope the results could help predict the long-term environmental consequences of current global warming.
The discovery was made by a team of scientists led by Professor Eske Willerslev and Professor Kurt H. Kjær. Professor Willerslev is a Fellow of St John’s College, University of Cambridge and Director of the Lundbeck Foundation Center for Geogenetics, University of Copenhagen where the geology expert Professor Kjær is also based.
Results from the 41 usable samples found hidden in clay and quartz are published today in Nature.
Professor Willerslev said: “A new chapter covering a further million years of history has finally been opened and for the first time we can look directly at the DNA of an ecosystem that has passed so far back in time.
“DNA can degrade quickly, but we’ve shown that under the right circumstances we can now go back further in time than anyone dared to imagine.”
Prof Kjær said: “The ancient DNA samples were found buried deep in sediments that had accumulated over 20,000 years. The sediments were ultimately preserved in ice or permafrost and, crucially, undisturbed by man for two million years.”
The incomplete samples, a few millionths of a millimeter long, were taken from the København Formation, a sediment deposit almost 100 meters thick nestled in the mouth of an Arctic Ocean fjord, far north of Greenland. The climate in Greenland at the time varied between arctic and temperate and was between 10 and 17°C warmer than Greenland today. Sediments accumulated meter by meter in a shallow bay.
Scientists have found evidence of animals, plants and microorganisms, including reindeer, hares, lemmings, birches and poplars. Researchers even found that Mastodon, an Ice Age mammal, wandered all the way to Greenland before later going extinct. Previously it was thought that the range of the elephant-like animals did not extend as far as Greenland from its known origins in North and Central America.
Detective work by 40 researchers from Denmark, UK, France, Sweden, Norway, USA and Germany revealed the secrets of the DNA fragments. The process was laborious – they first had to establish whether there was DNA hidden in the clay and quartz, and if there was, could they successfully detach the DNA from the sediment for the ‘examine ? The answer, ultimately, was yes. The researchers compared each DNA fragment with vast libraries of DNA from living animals, plants and microorganisms. A picture began to emerge from the DNA of trees, bushes, birds, animals and microorganisms.
Some of the DNA fragments were easy to classify as predecessors of present-day species, others could only be linked at the genus level, and some came from species that could not be placed in the DNA libraries of animals, plants and micro-organisms still living in the 21st century. .
The two-million-year-old samples are also helping scholars gain insight into a previously unknown stage in the evolution of DNA from a range of species still extant today.
Professor Kjær said: “Shipments are expensive and many samples were taken in 2006 when the team was in Greenland for another project, they have been stored since.
“It wasn’t 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. This means we were finally able to map a two-million-year-old ecosystem.”
Assistant Professor Mikkel W. Pedersen, co-first author of the paper and also based at the Lundbeck Foundation GeoGenetics Center, said: “The Kap København ecosystem, which has no current equivalent, existed at temperatures considerably higher than what we have today. and because, at first glance, the climate appears to have been similar to the climate we expect on our planet in the future due to global warming.
“One of the key factors here is how well species will be able to adapt to changing conditions resulting from a significant increase in temperature. The data suggests that more species can evolve and adapt at wildly varying temperatures than previously thought. But, importantly, these results show that they need time to do so. The rate of current global warming means that organisms and species don’t have that time , so the climate emergency remains a huge threat to biodiversity and the world – extinction is on the horizon for some species, including plants and trees.”
By examining ancient DNA from the Kap København Formation, the researchers also found DNA from a wide range of microorganisms, including bacteria and fungi, which they continue to map. A detailed description of how the interaction – between animals, plants and single-celled organisms – within the ancient ecosystem at the northernmost point of Greenland functioned biologically will be presented in a future research paper.
It is now hoped that some of the ‘tricks’ of plant DNA discovered two million years ago can be used to help make some endangered species more resilient to global warming.
Professor Kjær said: “It is possible that genetic engineering could mimic the strategy developed by plants and trees two million years ago to survive in a climate characterized by rising temperatures and prevent the extinction of certain species, plants and trees. This is one of the reasons why this scientific breakthrough is so important because it could reveal how to try to counter the devastating impact of global warming.”
The discoveries of the Kap København Formation in Greenland opened a whole new era in DNA detection.
Professor Willerslev explained: “DNA generally survives better in cold, dry conditions such as those that have prevailed for most of the time since the material was deposited at Kap København. Now that we have successfully extracted the Ancient DNA from Clay and Quartz It may be possible that clay may have preserved ancient DNA in hot, humid environments at sites found in Africa.
“If we can begin to explore the ancient DNA of clay grains from Africa, we may be able to gather groundbreaking information about the origin of many different species – perhaps even new insights into early humans and their ancestors – the possibilities are endless.”
Eske Willerslev, A 2-million-year-old ecosystem in Greenland discovered by environmental DNA, Nature (2022). DOI: 10.1038/s41586-022-05453-y. www.nature.com/articles/s41586-022-05453-y
Provided by the University of Cambridge
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