An article published in the journal “Nature” reports the identification of environmental DNA dating back to two million years ago discovered in sediments taken in the Kap København Formation in Greenland. A team of researchers led by Professors Eske Willerslev and Kurt H. Kjær used state-of-the-art technologies available for this type of exam.
Microscopic fragments of DNA were found for a total of 41 usable samples stored in clay and quartz within sediments that remained in the ice for two million years. The analysis of the samples revealed the presence of various species of plants and animals, not all identifiable with precision but nonetheless useful to get an idea of that ancient ecosystem.
Finding very ancient DNA is difficult because it degrades over time. Very cold environments such as Siberia help preserve the DNA of bones and teeth dating back hundreds of thousands of years. Environmental DNA, which ended up in sediments after, for example, an animal left fragments of skin or hair or a plant left fragments of leaves, in theory, can be preserved for longer by binding to other minerals. For this reason, the authors of this study examined sediment samples from the Kap København Formation.
The DNA samples taken were bound to clay and quartz that were part of sediments dating back to about two million years ago. The researchers estimate that those sediments formed over more than 20,000 years and were then buried in ice, where they remained undisturbed until the recent scientific investigations began.
The analysis of the recovered DNA fragments confirms the presence of hares and in the case of mitochondrial DNA of animals such as mastodons, reindeer, rodents, and geese, and various plant species. The discovery of mastodons in ancient Greenland comes as a surprise because paleontologists thought they didn’t come that far from North and Central America. The presence of marine species including horseshoe crabs and green algae indicates that the climate in Greenland was warmer than today.
The image (Courtesy Kjær, K.H., Winther Pedersen, M., De Sanctis, B. et al. All rights reserved) shows (a) taxonomic profiles of some species whose DNA was discovered in some of the samples taken in the Kap København Formation and (b) the phylogenetic placement of mitochondrial DNA belonging to or close to the Elephantidae family.
This type of study was made possible thanks to the latest developments in DNA extraction techniques and sequencing equipment. They made it possible to identify small and damaged DNA fragments present in sediments, and this opened up new research possibilities. In the case of the Kap København Formation, it allowed getting an idea of what the ecosystem was like in that area of Greenland two million years ago.
A crucial point of this study is the role of DNA binding with other minerals in its conservation. In hot and humid areas such as Africa, finding DNA from very ancient species has been impossible so far but now a new phase of research could open. Finding DNA from ancient humans in Africa could offer important new insights into human history.
