Academic Reading — Test 25

Reading passage

Across the wetlands of Denmark, Ireland, Germany, the Netherlands and Britain, peat cutters have for centuries made an unsettling discovery. Buried within the dark, waterlogged ground lie human remains so well preserved that the dead seem only recently to have died. These are the so-called bog bodies, and several hundred have now been catalogued from northern Europe. Some retain their skin, hair, fingernails and even the contents of their final meal. The most celebrated example, the Tollund Man found in Denmark in 1950, has facial features so serene and lifelike that the labourers who uncovered him initially believed they had stumbled upon a recent murder victim and alerted the police. The extraordinary state of these remains is not the result of any deliberate human technique but of the unusual chemistry of the peat bogs themselves. A raised bog is a strange and hostile environment for the bacteria and fungi that normally break down a corpse. Three conditions combine to halt decay. First, the water in the bog contains very little dissolved oxygen, which starves the aerobic micro-organisms that drive ordinary rotting. Second, the temperature of the deeper layers stays cold throughout the year, slowing whatever chemical activity remains. Third, and most importantly, the water is highly acidic, with an acidity comparable to that of vinegar, a condition that is deeply inhospitable to most forms of microbial life. The key chemical agent in the process is a substance released by the bog's dominant plant. As the moss known as Sphagnum dies and accumulates, it sheds a complex molecule called sphagnan into the surrounding water. Sphagnan performs several roles at once. It locks up the nitrogen that bacteria need in order to multiply, effectively denying them their food. It also reacts with the proteins of the body, a process similar to the tanning of animal hides into leather. This is why the skin of a bog body typically turns a deep brown and takes on a tough, leathery texture. The same reaction explains the reddish tint often seen in the hair, which is a chemical alteration of the original pigment rather than the natural colour the individual possessed in life. Preservation in a bog is, however, highly selective, and this is one of its most curious features. The acid that protects the soft tissues simultaneously attacks the hard ones. Bone is composed largely of calcium phosphate, a mineral that dissolves readily in acidic conditions. As a result, the skeleton of a bog body is frequently softened, distorted or removed altogether, leaving behind a flattened figure of skin draped over little or no internal support. The outcome is therefore the reverse of what happens in a dry tomb or a desert grave, where the bones survive while the flesh disappears. In the bog, the flesh endures and the bones may vanish. The same chemistry that preserves the body also offers a remarkable window onto the past. Because stomach and intestinal contents are sometimes intact, researchers have been able to reconstruct the final meals of people who lived two thousand years ago, identifying seeds, grains and wild plants gathered shortly before death. Many of the better-preserved individuals appear to have met violent ends. Some were hanged, others had their throats cut, and a number show signs of having been struck or restrained. Scholars continue to debate why. The injuries may point to ritual sacrifice connected with the religious beliefs of Iron Age communities, to the execution of criminals, or to the punishment of those accused of wrongdoing. The bogs of the period were often regarded as sacred thresholds between the world of the living and that of the supernatural, which lends some weight to the sacrificial interpretation, though no single explanation accounts for every case. For modern archaeology, the bog bodies present both an opportunity and a problem. Once a body is lifted from the ground and exposed to air, the conditions that protected it for millennia are abruptly reversed, and decay can set in within hours. Conservators must therefore act quickly, and the techniques used to stabilise the remains are demanding and not always successful. Several bodies recovered in earlier centuries were lost because no method existed to preserve them outside the bog. Today, careful chemical treatment and controlled storage allow the most important finds to be kept for study and display, ensuring that these silent witnesses continue to inform our understanding of the distant past.