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| Reconstruction of the Kap København Formation ecosystem 2 million years ago. Image credit: Beth Zaiken. |
The Kap København Formation is located in Peary Land, North Greenland, in what is now a polar desert.
Previous research suggests that the region had a much warmer climate around 2-3 million years ago with temperatures more than 10 degrees Celsius warmer than today.
However, the biological communities inhabiting the Arctic during this time remain poorly understood because vertebrate fossils are rare.
In the new study, Professor Eske Willerslev, a researcher at the University of Copenhagen, the University of Cambridge and the University of Bremen, and colleagues extracted and sequenced environmental DNA (eDNA) from 41 organic-rich sediment samples taken from 5 different sites within the Kap København Formation.
“DNA can degrade quickly but we’ve shown that under the right circumstances, we can now go back further in time than anyone could have dared imagine,” Professor Willerslev said.
“The ancient eDNA samples were found buried deep in sediment that had built-up over 20,000 years.”
“The sediment was eventually preserved in ice or permafrost and, crucially, not disturbed by humans for two million years.”
From the eDNA, the scientists were able to build a picture of the ancient ecosystem: an open boreal forest with a mixed vegetation of poplar, birch and thuja trees, as well as a variety of Arctic and boreal shrubs and herbs.
The eDNA record also confirms the presence of hares, and mitochondrial DNA from the site points to the presence of other animals including mastodons, reindeer, rodents and geese.
“The eDNA we collected is considerably older than any previously sequenced DNA,” said Dr. Alan Hidy, a researcher at Lawrence Livermore National Laboratory.
“Our results detected five times as many plant varieties as previous studies using shotgun sequencing of ancient sediments, which is well within the range of the richest northern boreal metabarcoding records.”
The ancient eDNA was also recovered from marine organisms and suggests the presence of a population of the Atlantic horseshoe crab (Limulus polyphemus).
The authors propose that this could mean that there were warmer surface water conditions in the Early Pleistocene at Kap København, which is consistent with previous estimates.
The findings demonstrate the potential to use ancient environmental DNA to track the evolution of biological communities two million years ago.
“The Kap København ecosystem, which has no present-day equivalent, existed at considerably higher temperatures than we have today — and because, on the face of it, the climate seems to have been similar to the climate we expect on our planet in the future due to global warming,” said Dr. Mikkel Pedersen, a researcher at the Lundbeck Foundation GeoGenetics Centre.
Sources
K.H. Kjær et al. 2022. A 2-million-year-old ecosystem in Greenland uncovered by environmental DNA. Nature 612, 283-291; doi: 10.1038/s41586-022-05453-y
