Study Suggests Bones Preserved in Peat Bogs May Be at Risk

Per the paper, archaeologists need to act quickly to recover organic material trapped in the wetlands before specimens degrade

Tollund Man
Bogs are perhaps best known for preserving prehistoric human remains. One of the most famous examples of these so-called "bog bodies" is Tollund Man. Getty Images

Peat bogs are notoriously uninhabitable. When low in oxygen, they don’t support microbial life, and without microbes, dead humans and animals caught in the spongy wetlands fail to decompose. Thanks to this unusual characteristic, peat bogs have long been the scene of incredible archaeological discoveries, including naturally mummified human remains known as bog bodies.

But new research published in the journal PLOS One presents evidence that bogs are losing their body-preserving abilities. As Cathleen O’Grady reports for Science magazine, archaeologists found that the best-preserved artifacts recovered from bogs in 2019 resemble the worst-preserved ones found in the 1970s, while the best-preserved specimens from the ’70s are on par with the worst retrieved in the 1940s. (Bogs’ lack of oxygen, as well as an abundance of weakly acidic tannins, preserves artifacts as delicate as small mammal and bird bones.)

The findings suggest that archaeologists may need to act quickly to uncover what’s left in the world’s bogs.

“If we do nothing, wait and hope for the best, it is likely that the archaeo-organic remains in many areas will be gone in a decade or two,” the authors say in a statement. “Once it is gone there is no going back, and what is lost will be lost forever.”

Northern Europe is dotted with peat bogs, which stood out among the thickly forested prehistoric landscape and may have served as spiritual places. “Half earth, half water and open to the heavens, they were borderlands to the beyond,” wrote Joshua Levine for Smithsonian magazine in 2017.

Many bog bodies show signs of horrific violence. Theories regarding these unlucky individuals’ deaths—and unusual mode of interment—range from execution to robberies gone wrong and accidents, but as archaeologist Miranda Aldhouse-Green told the Atlantic’s Jacob Mikanowski in 2016, the most likely explanation is that these men and women were victims of ritualized human sacrifice.

Study Suggests Bones Preserved in Peat Bogs May Be at Risk
Researchers compared artifacts recovered from bogs in the 1970s and 1940s with specimens found in 2019. Boethius et al.

The new study focuses on the Ageröd bog in southern Sweden. To date, excavations at the site have unearthed carved deer and boar bones, arrowheads, and fishing net sinks associated with Mesolithic people who lived in the region more than 8,000 years ago. These artifacts often look “as if they had been laid down the day before yesterday,” lead author Adam Boethius, an archaeologist at Lund University, tells Johanna Hellström of Sveriges Radio.

In 2019, Boethius and his colleagues uncovered 61 bog artifacts with clear signs of wear. They were lighter than expected, explains Sophie Bates for Forbes, and their once-detailed carvings and features were difficult to discern.

The researchers compared their finds with more than 3,700 artifacts discovered in the 1940s and ’70s. Though these earlier excavations had yielded small bones, the 2019 excavations did not, suggesting the delicate objects have experienced accelerated degradation in recent decades.

Per the paper, the team suspects that human activities like excavation and farming have introduced oxygen into the bog’s watery mix. When the element reacts with chemicals in the bog, it creates sulfuric acid, which is highly corrosive. Drought and flooding caused by climate change may have exacerbated the situation further.

Benjamin Gearey, a wetland archaeologist at University College Cork who wasn’t involved in the study, tells Science that the results are “sobering,” demonstrating the “catastrophic loss of irreplaceable organic archaeological remains” in European wetlands.

“[N]othing ‘special’ has happened to the Ageröd site,” the authors write in the study, so the same level of degradation may be occurring at bog sites throughout Europe.

As the archaeologists conclude in the statement, “If the organic remains deteriorate, these type of analyses will not be possible to do anymore, and given the information we are now generating from them, it will be a devastating blow to our understanding of ancient cultures, diet and subsistence strategies, migration and mobility.”