On the frozen northernmost tip of Greenland lies a unique geological formation called the Kap Köbenhavn Formation. This region, deep in the Arctic Circle, has one of the coldest and driest environments on Earth.
However, 2 to 3 million years ago, this was a very different place from what it is now. At that time, the average minimum temperatures in summer and winter were 10°C and 17°C respectively, more than 10°C higher than the current temperature.
While scientists have intensively surveyed the geological deposits of Arctic strata for nearly 40 years, little is known about the biomes that inhabited the Arctic during this period due to the sparse fossil record.
Recently, an international research team of more than 40 scientists published a new study in the journal Nature. They report the extraction of the oldest environmental DNA (eDNA) to date after analysis of clay and quartz samples from the deposit.
How long can DNA exist?
Obviously, DNA won’t last forever. It decays steadily over time, the rate of which depends on the surrounding environment.
Past research has shown that under environmental conditions such as deep-frozen permafrost, DNA fragments should be preserved for more than a million years. In 2021, a team of scientists conducted DNA analysis on three mammoth teeth found in Siberia buried in permafrost and discovered ancient DNA that was millions of years old.
The frozen sediments of the Kap Köbenhavn Formation are an ideal environment for preserving ancient DNA. The new study, by analyzing samples from this sediment, has a new surprise: They found that the DNA in these samples can be traced back to more than 2 million years ago, which broke the previous record for the oldest DNA and set the time limit once again. Go forward 1 million years.
The researchers noticed that these DNA molecules were somehow protected from the ravages of time by binding to the surface of the clay particles, allowing the DNA to survive as free molecules in the sediment far longer than in the bones of the animals they originally belonged to. middle.
an extinct ecosystem
In the new study, the researchers pieced together tiny pieces of DNA and compared each one to a vast library of DNA collected from modern animals, plants and microbes.
This is a very challenging task. First, they needed to determine whether DNA was lurking in the clay and quartz samples. Next, they need to determine how to successfully isolate this DNA from the sediment for detection.
Through DNA identification and comparison, researchers quickly classified some DNA fragments as the ancestors of certain modern species (such as reindeer, geese, hares and lemmings); others were DNA traces of plants, such as birch trees , poplar, as well as algae and other microorganisms.
An international research team of up to 40 scientists has published a new study in the journal Nature. They report the extraction of the oldest environmental DNA (eDNA) to date after analysis of clay and quartz samples from the deposit.
But not all DNA fragments can be used for species positioning. Some DNA can only be associated at the “genus” level, and some DNA fragments cannot be matched with any modern known species at all.
Interestingly, they also found genetic traces of an extinct elephant-like creature – the mastodon. Before that, no one knew that the mastodon had set foot in Greenland…
Finally, the researchers drew a completely different picture. Based on the ecosystem of the modern world, it has drawn a DNA map of the plants, animals and microorganisms that lived in the Kap Köbenhavn formation more than 2 million years ago.
see the distant past
The most exciting part of the study, though, isn’t just that it discovered a species, it’s what it tells scientists about how these species coexisted in prehistoric ecosystems that were much warmer than they are today. Knowing this information is crucial to our understanding of how biodiversity might be affected during periods of warming, and how a warmer climate might drive evolution.
We know that the DNA inside the cells of all living things mutates slowly, as environmental changes drive adaptation and evolution to occur between generations. However, we rarely have the ability to go straight back in time to observe previous DNA molecules.
Now, with this ancient DNA, scientists have finally opened a new chapter in a history spanning 1 million years, seeing directly for the first time the DNA of an ecosystem in the distant past. This means that scientists can now directly observe the process of molecular evolution in depth, recover and directly study the molecules formed in animals and plants 2 million years ago, without being limited to the current genetic information of modern species.