22 February 2020 | New Scientist | 9THE last time humans came up
against rising seas due to major
global warming they tried to
protect themselves by putting
up physical barriers and possibly
appealing to divine powers to hold
back the water.
Following the last glacial
maximum 21,000 years ago,
Earth warmed by about 3 to 5°C
over thousands of years, probably
due to a slight change in its orbit
that increased sunshine exposure.
This melted ice sheets that once
covered much of North America
and northern Europe and raised
global seas by about 120 metres
to today’s levels.
There are no written accounts
of this period, as writing was
invented only about 5000 years
ago. But Patrick Nunn at the
University of the Sunshine Coast
in Australia has found clues to how
our ancestors coped with sea level
rise in oral histories that may have
been passed down for hundreds
of generations.
In Australia, for example,
a quarter of the continent was
swallowed by the rising ocean
between 18,000 and 8000
years ago. At least 26 Aboriginalgroups living in coastal areas seem
to have preserved stories of their
ancestors’ experiences.
In one story told by the
Wati Nyiinyii people of southern
Australia, their ancestors tried
to block the incoming water by
stacking bundles of thousandsof spears along the coastline.
In a story told by the Gunggandji
people of north-east Australia,
their ancestors heated boulders
with fire and rolled them down
cliffs into the water (Norois,
doi.org/dmsg).
The fact that so many groups
have stories of sea level rise
suggests it was transformational
enough to warrant being
described to hundreds of
subsequent generations,
says Sean Ulm at James Cook
University in Australia. “Although
there is scepticism that oral
histories record events more than
a couple of hundred years old,
the evidence for Aboriginal oralhistories documenting sea level
rise more than 8000 years ago
is compelling.”
Efforts to prevent sea level
rise weren’t limited to Australia.
Seas continued to rise in the
Mediterranean until about 6000
years ago. Divers off the coast of
Israel recently discovered a stone
wall built about 7000 years ago,
seemingly to protect the ancient
village of Tel Hreiz from flooding.
In France, the Carnac stones –
parallel rows of stones along the
Brittany coast thought to be more
than 6000 years old – may also
have been laid down to ward off
rising seas, says Nunn. The stones
have previously been interpreted
as astronomical symbols or
graveyards, but these explanations
haven’t held up to scrutiny, he says.
Spiritual offerings may have
been another way that people
tried to resist sea level rise, says
Nunn. He believes neatly arranged
collections of stone tools and
human remains that have been
found along the north-west coast
of Europe were placed there to “try
to persuade the gods to stop the
sea level from continuing to rise”.
Ulm says this is certainly
possible, but it is hard to interpret
the motivations of people in the
distant past.
Ultimately, these attempts
were futile. In Australia, the
coastline contracted by about
140 kilometres. In Israel, Tel Hreiz
was submerged. Legends also tell
of cities like Ys in France, Cantre’r
Gwaelod in Wales and Dvārakā
in India that disappeared
underwater. Though these may
not represent literal cities, they
may be based on memories of
real places that were drowned
by rising seas, says Nunn. ❚LOUIS- M
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DESE
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MAGESWere the Carnac stones
in France an attempt to
ward off rising seas?8000
The minimum age of some
sea level rise stories, in yearsAstronomy
Stuart Clark
RADIO waves blasting out of a
red dwarf star have an unusual
source – an orbiting planet.
Astronomers using the Low-
Frequency Array radio telescope
in the Netherlands have discovered
that red dwarf star GJ 1151 is
emitting radio signals consistent
with the star possessing a roughly
Earth-sized planet completing a
full orbit every few days.
A planet orbiting at this distance
would probably be in a star’s
habitable zone, the region in which
temperatures allow for liquid water
to flow on the planet’s surface.
However, the star is generating
radio waves because the orbiting
planet passing through its magnetic
field acts like an electric dynamo.
The strength of the waves shows
that substantial electrical power is
flowing between the star and the
planet, which will heat up the
planet’s atmosphere. It could even
be boiling the atmosphere away,
rendering the world uninhabitable
(Nature Astronomy, doi.org/dmst).
Harish Vedantham at the
Netherlands Institute for Radio
Astronomy, who led the work, says
there is considerable uncertainty
about the size and mass of the
planet, so it is hard to say what is
happening with the atmosphere.
But the discovery suggests radio
astronomy could be a good method
for detecting exoplanets, he says.
The next step is to attempt
to detect this planet through its
gravitational pull on the star, which
would cause it to wobble slightly.
This would provide better estimates
of the planet’s mass and orbit,
and let us figure out the condition
of its atmosphere.
The team is also looking at
radio data from other stars in an
effort to locate further planets.
Other detection methods have
found numerous planets around
red dwarfs, and the stars generally
have strong magnetic fields. ❚
Exoplanet generates
radio waves from
its red dwarf sun
Ancient humansAlice KleinHow our ancestors tried
to battle sea level rise