Two million-year-old DNA fragments were detected in the frozen layers of Arctic sediments. This ancient genetic material, the oldest ever discovered, depicts a previously unrecognized ecosystem.
Since 2006, researchers have discovered 41 DNA samples within a 100-meter-deep sediment sheet in the Copenhagen Cape Formation in northern Greenland. These genetic fragments, which are known as environmental DNA, were left over from plants, animals and microbes that once lived in this area and were well preserved by the frozen soil and arctic ice.
The oldest known previous DNA sample, announced in 2021, was recovered from a 1.2-million-year-old mammoth bone in Siberia, the researchers wrote in a statement. In a new study published on December 7 in the journal Nature, researchers isolated and analyzed ancient DNA samples. They compared the ancient DNA with known genome sequences to determine what organisms they belonged to.
The results paint a picture of a very diverse ecosystem that includes birds, reindeer, rabbits and, most amazing of all, mastodons. Mastodons are an extinct group of elephant relatives that were previously unknown to have also lived in those northern regions. Willerslow piersaid the study’s lead author and an evolutionary ecologist from the University of Cambridge in the UK.
A new chapter spanning more than a million years of history has finally opened, and for the first time we can look directly at the DNA of an ecosystem dating back so far.
An artist’s impression of a newly discovered ecosystem in Greenland that existed two million years ago. DNA samples show that reindeer, rabbits, birds and mastodons roamed the area.
Another artist’s impression of the Cape Copenhagen ecosystem two million years ago
DNA fragments were very difficult to study. The researchers wrote in their statement that each piece of genetic material was only a few millionths of a millimeter long, making it very difficult to separate the DNA pieces from the sediment layer without breaking them.
Sediment collection started in 2006; But the researchers decided to wait until more advanced technologies became available before attempting to extract the DNA. When a new generation of DNA extraction and sequencing equipment became available to researchers, they succeeded in extracting and identifying very small and damaged pieces of DNA.
In addition to various animals, ancient DNA revealed the presence of several species of trees, bacteria and fungi. Not all DNA samples could be matched to known species. This suggests that some may be new to science; Although almost all were correctly identified at least to the genus level.
The sediment layer that the researchers explored was formed over a period of 20,000 years, about two million years ago. At that time, the temperature of the region was 10-17 degrees Celsius warmer than today’s Greenland. This shows that ecosystems can completely disappear or appear due to temperature changes.
Researchers removing sediment samples from the Cape Copenhagen formation in northern Greenland
As the sediments piled up over time, tiny pieces of DNA became trapped in them.
Eske Willersloh at the University of Copenhagen prepares DNA samples for analysis.
Mikel Pedersenone of the authors of the article and an expert in evolutionary genetics from the University of Copenhagen said:
The data show that more species can evolve and adapt to extreme temperature changes than previously thought; But more importantly, the results show that they need time to do so. Therefore, species that are currently at risk due to climate change and the result of human activities are unlikely to achieve such success; Because they will have much less time to adapt.
Researchers are trying to paint a deeper picture of the Cape Copenhagen ecosystem by examining how species might interact with each other. Also, the new findings could provide insights into how DNA has changed over the past two million years.
The ability to locate and isolate and sequence such ancient DNA raises the prospect that ancient genetic samples of this age, or perhaps even older, can be found around the world. Willerslow said:
If we can begin to explore ancient DNA, we may be able to gather groundbreaking information about the origins of different species, and perhaps even gain new knowledge about early humans and their ancestors.