SCIENCE sciencemag.org 31 JANUARY 2020 • VOL 367 ISSUE 6477 503Putting those maps together with the
sheer number of samples emerging from
the North Sea, researchers are beginning to
answer a question particularly relevant to
humanity’s future: What do people do when
sea levels rise?
About 8500 years ago, a massive fresh-
water lake in North America called Lake
Agassiz, formed by melting glaciers,
drained suddenly into the sea. What had
been gradual sea-level rise accelerated, and
seas rose a few meters within decades. Dog-
gerland transformed from a temperate, for-
ested plain into an estuarial wetland dotted
by drier highlands. Core samples collected
along river valleys by the Lost Frontiers
team traced the flooding, amounting to a
“transect through time,” Gaffney says.
To explore the impact on people,
Amkreutz analyzed dozens of human bones
dragged up by fishing boats as well as finds
plucked off the Zandmotor and other Dutch
beaches. He traced the bones to 18 offshore
sites around the prehistoric Rhine River es-
tuary and dated them with radiocarbon to a
precision of about 100 years; all were about
8500 years old.
He and Niekus then used chemical sig-
natures from collagen preserved in dozens
of the bones to analyze what people in
Mesolithic Doggerland were eating before
and during that transition. As the land-
scape changed, the diet of its residents did,
too, shifting from land animals to fresh-
water fish. “It shows their flexibility in the
face of climate change,” Amkreutz says.
“They didn’t leave as sea levels rose; they
changed their diet.”Eventually, that, too, came to an end. On
the basis of sediments and computer mod-
els, researchers think a tsunami originating
off modern-day Norway around 6150 B.C.E.
devastated Doggerland with waves at least
10 meters high. Soon the landscape van-
ished as global sea levels continued to rise.
At his lab at the University of Warwick,
Robin Allaby is tracing the changes by
searching 60 of the core samples collected
by Gaffney and his team for what’s called
environmental DNA, shed into water and
soil by ancient species. The team scoops
up and analyzes all the DNA in a sample,
using next-generation sequencing methods
that capture millions of DNA fragments,
and compares it with libraries of known
genomes. “The surprising thing is just how
much DNA is still down there,” Allaby says.
The results chronicle changes in Dogger-
land’s ecosystems as seas rose.In the older, earlier layers, “We can see
quite a broad range of DNA that’s clearly
terrestrial,” he says. Allaby has picked out
terrestrial species, including bears, boars,
birds, spiders, and mosquitoes. He has iden-
tified plant species, too, including hazel and
linden trees and meadow grasses. “It’s obvi-
ously a lowland, very fertile and probably
more attractive than the British uplands
and adjacent Europe,” he says.
Higher up, in the younger core samples,
the DNA tells a tale of inexorable transfor-
mation. “We can see the rise of an estuarine
environment and a slow switch to marine
taxa,” Allaby says, as bears and boars give
way to sea grasses and fish.
Researchers say the techniques being pio-
neered or perfected in the North Sea could
be applied to far-flung hot spots of human
migration, including Beringia and the wa-
ters that surround the archipelagos of Ocea-
nia. “There are big questions about human
dispersal and development which can only
be answered by looking at submerged land-
scapes,” Bailey says. “These same landscapes
were probably good places to provide step-
ping stones into new territory.”
At the end of van Wingerden’s afternoon
walk, all she had to show for 2 hours of
searching were a few pieces of animal bone
and a wide smile. But the next day, her luck
turned. Tucked in among a pile of seashells,
she found a carefully worked tool with char-
acteristic Neanderthal handiwork, dating
back at least 45,000 years: one more piece
of a lost landscape, rediscovered. jPHOTO: MANON BRUININGA Andrew Curry is a journalist in Berlin.
This 13,000-year-old skull fragment of a modern
human was fished up off Rotterdam, the Netherlands.Published by AAAS