Today, it could be a barren Arctic desert; however, the oldest known DNA revealed that Greenland was a lush landscape of trees and vegetation with an array of animals, even the now-extinct mastodon.
In the study published in Nature, the researchers were able to find possible match species to an ancient environmental DNA (eDNA) record describing the rich plant and animal assemblages of the Kap København Formation in North Greenland in Peary Land, dated to around two million years ago. Today, the area is a polar desert.
According to Willerslev, the study’s senior author, the area has gone through a climate change event that occurred millions of years ago. The sediment found in the area probably accumulated for thousands of years before the climate cooled, which helped preserve the delicate DNA components in the samples.
The warm period that occurred in the region provided the area with abundant animal and plant life. The record shows an open boreal forest ecosystem with mixed vegetation of poplar, birch, and thuja trees, as well as a variety of Arctic and boreal shrubs and herbs.
In addition, the presence of marine species, including horseshoe crabs and green algae, supports a warmer climate than today.
Finding animal fossils can be very hard; many of these species had not previously been detected at the site from macrofossil and pollen records.
However, Scientists were able to extract environmental DNA (eDNA) from the soil.
“The study opens the door into a past that has basically been lost,” said lead author Kurt Kjær, a geologist and glacier expert at the University of Copenhagen.
eDNA is the genetic material that organisms shed into their surroundings and can be found in various forms, such as waste, hair, and carcasses. This allowed them to identify organisms that live in the environment.
Unfortunately, studying ancient DNA can be challenging since the genetic material often degrades with time owing to microbial enzymatic activity, mechanical shearing, and spontaneous chemical reactions such as hydrolysis and oxidation.
According to Eske Willerslev, the researchers were able to analyze the genetic information contained in damaged DNA using the latest technologies.
The survival of such ancient eDNA relates to its binding to mineral surfaces. Adsorption at mineral surfaces modifies the DNA conformation, probably impeding molecular recognition by enzymes, which effectively hinders enzymatic degradation.
The DNA samples collected from the region also confirm the presence of hare and mitochondrial DNA from animals, including reindeer, rodents, and geese, all ancestral to their present-day and late Pleistocene relatives.
One of the most surprising DNA samples that the researchers found was the DNA of a mastodon, an extinct species that looked similar to a mammoth.
By pulling dozens of species out of just a few sediment samples, the study highlights some of eDNA’s advantages, said Benjamin Vernot, an ancient DNA researcher at Germany’s Max Planck Institute for Evolutionary Anthropology who was not involved in the study.
“You really get a broader picture of the ecosystem at a particular time,” Vernot said. “You don’t have to go and find this piece of wood to study this plant, and this bone to study this mammoth.”
The findings open new areas of genetic research, demonstrating that it is possible to track the ecology and evolution of biological communities from two million years ago using ancient eDNA.
Stockholm University’s Dalen, who worked on the study that previously held the “oldest DNA” record from a mammoth tooth around a million years old, expects ancient DNA research to keep pushing deeper into the past.
“I wouldn’t be surprised if you can go at least one or perhaps a few million years further back, assuming you can find the right samples,” Dalen said.
