Archaeology Magazine - March/April 2023 - 62

LETTER FROM THE FAROES
A team of paleoclimatologists led by Columbia University's William J. D'Andrea (left)
prepares to extract a sediment core from a lake on the island of Eysturoy.
Back in the laboratory, Curtin
began analyzing the core. She found
that abundant fecal biomarkers from
domesticated animals appeared suddenly
in sediments that dated to
around a.d. 500. This was a clear signal
that people had lived near the location
of the lake at that time.
Strangely, radiocarbon dates from
samples taken from higher up in the
core were not more recent than a.d.
500 as would be expected, but were
as much as 4,000 years old. " There's
this whole interval in the core where
you can't rely on the radiocarbon dates
anymore, " says D'Andrea. " The simplest
explanation is that when people
showed up, they cut peat for fuel that
contained old leaves and other ancient
material. Some of this material was
washed into the lake, so they introduced
old carbon trapped in the peat
into the sediments right after the sheep
arrived. " Despite these anomalous
dates, the identification by College of
William & Mary paleoclimatologist
Nicholas Balascio of a layer of volcanic
ash in the core dating to a.d. 875 gave
the team confidence that their radiocarbon
modeling was accurate.
The team now had at least two
independent lines of evidence that
62
pointed to early settlement, but they
weren't satisfied. They aimed to identify
the species of animal that was the
source of the fecal biomarkers. " We
wanted to put the nail in the coffin of
this discussion, " says Curtin, " and we
needed one more line of evidence. "
The team sent soil samples from
the core to the laboratory of geneticist
Beth Shapiro at the University of California,
Santa Cruz, and asked her team
to isolate mammalian DNA signatures.
After many attempts, biologist Sabrina
Shirazi was able to identify genetic
sequences of mammals in the Faroese
sediments. " I've worked with a lot of
ancient and modern environmental
DNA samples, and with any soil sample
the majority of DNA is going to
be fungal and bacterial, " says Shirazi.
" Any DNA from mammals or other
animals is going to be present in trace
amounts, and that might mean you
are getting 200 sequences assigned to
a species in a sample-and that's on the
high side. " The Faroese samples were
different. " It was the most I had ever
seen for a vertebrate in any sample, on
the order of a couple hundred thousand
reads assigned to sheep in each
of the samples. " Shirazi had identified
another indicator that sheep were
in the Faroes beginning in the fifth
century a.d., and the data aligned perfectly
with the fecal biomarkers, all of
which indicated the presence of a large
number of sheep at the site through
time. " It was sheep, sheep, sheep, " says
Shirazi. Plant DNA in the samples
also showed that woody plants disappeared
on the island around the same
This lake, which covers a ninth-century a.d. Viking site known as Argisbrekka,
contains sediments showing that people lived there as early as a.d. 500.
ARCHAEOLOGY * March/April 2023
Archaeology Magazine - March/April 2023

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