NEW YORK — Ancient DNA coaxed from sediments found in what is now a polar desert in northern Greenland hints that the same site 2 million years ago was a more boreal environment with a range of vegetation and animals like reindeer and mastodons.
In an analysis that took years, an international team of researchers isolated environmental DNA from clay and quartz samples collected at the Kap København Formation, a sediment deposit in the northernmost reaches of Greenland. These samples, dating back 2 million years, now represent the oldest DNA samples, surpassing the record by about 1 million years.
Eske Willerslev from the universities of Copenhagen and Cambridge and colleagues sequenced these ancient eDNA samples and compared them to reference genomes of modern-day plants and animals to piece together a picture of what lived in that region of Greenland when the climate was more than 10 degrees Celsius warmer than today. Nor did they report in Nature on Wednesday, they found an ecosystem unlike any present on Earth today that combines elements of boreal and Arctic climates and, surprisingly, was home to mastodons.
“It is actually a climate which is very similar to what we expect to face on Earth due to global warming,” Willerslev said during a press briefing. “And therefore, of course, it gives us some kind of idea [of] how can nature respond to increasing temperatures?”
The Kap København Formation stands at the mouth of a fjord and includes both clay and quartz sediments from the marine and coastal environments. The researchers found that DNA could be preserved by binding to the quartz and clay minerals present in the sediments, although they were able to isolate more DNA that had been adsorbed to quartz.
In all, they extracted DNA from 41 different sediment samples from five different sites at the formation. After screening the samples for either plastid DNA or mitochondrial DNA, the researchers sequenced them and compared their resulting sequences against datasets of modern animals, plants, and microorganisms.
Through their analysis, the researchers uncovered about 102 plant genera and nine different animal taxa. Because their samples were so old, the researchers often could only resolve the organisms to the family or genera level, if at all. Willerslev noted that these taxa likely represent the ones that were the most abundant in the area.
The samples still contained surprises. One of the animal taxa the researchers identified was a mastodon, whose range was not known to extend to Greenland from its home of North and Central America. Additionally, the researchers uncovered snippets of horseshoe crab DNA, which generally live today in warmer waters.
These findings begin to put together a picture of life at this location 2 million years ago, which the researchers noted has no modern analog. Some plant taxa — such as spruce and poplar — suggest a boreal environment, although others reflect a more Arctic environment.
Today, Willerslev said, this region is barren and home to moss, lichen, and muskox.
“Therefore it was super exciting, when we recovered the DNA, that a very, very different ecosystem appeared,” he noted.
Having a better understanding of the organisms that lived in northern Greenland 2 million years ago when the climate was much warmer could also inform efforts to shield modern organisms from the effects of climate change. The researchers added that while their data show that organisms in Greenland were able to evolve and adapt to a warmer climate, climate change will occur at a much faster rate, giving organisms minimal time to adapt.
According to the researchers, some organisms, especially plants, could be genetically engineered to better withstand those changes. “We have a genetic roadmap of how taxa react to climatic changes,” Willerslev said, adding that this map could be applied to make taxa more resilient.