A sunken landmass that connected Britain to mainland Europe until a few thousand years ago may have been an excellent refuge for plants and animals, including humans, during last ice agefinds a new study.
Parts of Doggerland, now submerged under the North Sea, hosted temperate forests as early as 16,000 years ago – long before such forests recolonized Britain and north-west Europe after the glaciers’ final retreat around 11,700 years ago.
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Oaks (Quercus), elm (Ulmus) and hazel trees (Corylus) thrived for millennia in southern Doggerland, where the new study was conducted, before the land mass disappeared. Previous estimates suggested that Doggerland was completely flooded 7,000 years ago, but the new results indicate that this may have happened closer to 6,000 years ago. Scientists reconstructed the region’s long-lost terrestrial ecosystem using DNA which was preserved in dirt under the sea for thousands of years, known as ancient sedimentary DNA.
“We have evidence of wild boar, deer, bears, aurochs,” lead author of the study Robin Allabyan evolutionary geneticist and professor of genomics at the University of Warwick in the United Kingdom, told LiveScience. “But to my knowledge, it’s the largest sedimentary DNA study ever done.”
Allaby and his colleagues analyzed 252 samples from 41 cores they drilled from under the North Sea off the coast of England. Specifically, the researchers took the cores along the prehistoric, 20-mile-long (30-kilometer) Southern River, located in what was once southern Doggerland.
Scientists have long known that Doggerland was forested before it was flooded by the North Sea. But the age of these forests was unclear, so the researchers assumed they appeared around the same time as the forests of Great Britain. The consensus before this new research was that 16,000 years ago, southern Doggerland was tundra (a dry, treeless plain), not forest, Allaby said. At that time, the ice sheets reached down to what is now the border between Scotland and England, he added.
The researchers analyzed sediments in the cores and divided them into two categories: safe and unsafe. Safe sediments were fine silt and clay that contained ancient DNA from species that lived in the area where the core was taken. Uncertain sediments were coarser sands and gravels that contained ancient DNA that was discarded far from where the core was extracted, meaning that this DNA was not useful for reconstructing the local ecosystem.
“It just makes perfect sense,” Allaby said, as “DNA doesn’t survive long in water.” Sediments are usually transported and deposited in fluid, with slow-moving water picking up only fine sediments and fast-moving, higher-energy waters displacing coarser sediments. Slow-moving water can transport sediments carrying DNA only short distances before the DNA is rapidly degraded. Fast-moving water, on the other hand, can transport sediments with DNA much further before it dissolves.
This means that when the researchers found fine sediments with old DNA in the cores, it was likely that this DNA was discarded locally. DNA in coarse sediments was likely from upstream ecosystems. Therefore, “we could pick out the samples that we wouldn’t trust to tell us about the local environment,” Allaby said.
Ancient DNA in safe sediments showed that temperate trees and woodland animals lived around the Southern River starting around 16,000 years ago, when large parts of northwestern Europe and Britain were still covered in tundra. Remarkably, the researchers identified DNA from a walnut relative (Pterocarya) which was thought to have been extirpated from the region 400,000 years ago. The team also found traces of heat-loving linden trees (Tilia), which suggests that southern Doggerland was milder than the surrounding areas during the last ice age.
“Our knowledge is very imprecise, as it turns out,” Allaby said. “This isn’t pure tundra—there’s enough of an environment here to sustain something that looks like a forest.”
The results, published on March 10 in the journal PNASsuggests that Stone Age humans would have had “a lot to live on” in southern Doggerland after ice sheets retreated from the area about 21,000 years ago, Allaby said. “We can predict how good places for settlement will be, and typically at the mouth of rivers is the place to go, because you’re close to resources.”
The findings may also help resolve Reid’s paradox, which describes the mismatch between seed dispersal rates and how quickly trees such as oaks recolonized northern areas from further south after the last ice age, the researchers said. Southern Doggerland or another nearby region, such as northern France, may have been a glacial “micro-escape” for temperate trees, allowing species to spread north much faster than they could have if they had only survived on the Iberian Peninsula, for example.
Finally, the study indicated that the North Sea was completely submerged in southern Doggerland around 6,000 years ago, which is at least 1,000 years earlier than previous estimates of when the land mass was flooded.
“It’s another highlight of the inaccuracy of what our knowledge is about this landscape,” Allaby said. “There really is a limit.”
Allaby, R.G., Ware, R., Cribdon, R., Hansford, T.A., Kinnaird, T., Hamilton, D., Kistler, L., Murgatroyd, P., Bates, R., Fitch, S., & Gaffney, V. (2026). Early pre-Flood colonization consistent with northern glacial brefugia in southern Doggerland revealed by sedimentary ancient DNA. Proceedings of the National Academy of Sciences, 123(11), e2508402123. https://doi.org/10.1073/pnas.2508402123
