Bog bodies, also known as bog people, are preserved human bodies found in sphagnum bogs in Northern Europe, Great Britain and Ireland. Unlike most ancient human remains, bog bodies have retained their skin and internal organs due to the unusual conditions of preservation. Under certain conditions, the acidity of the water, the cold temperature and the lack of oxygen combine to tan the body's skin: skeletal preservation is very rare in these bodies, as the acid in the peat dissolves the calcium phosphate of bone. The bodies provide very useful research material for archaeologists. Some of the bodies retain intricate details like tattoos and fingerprints. Fingerprint expert C.H. Vogelius Andersen was astonished to find that Grauballe Man's hand prints were clearer than his own. The stubble and facial features of Tollund Man are particularly well preserved.
The bog chemistry environment involves a completely saturated acidic environment, where considerable concentrations of organic acids and aldehydes are present. Layers of sphagnum and peat assist in preserving the cadavers by enveloping the tissue in a cool immobilizing matrix, impeding water circulation and any oxygenation. An additional feature of anaerobic preservation by acidic bogs is the ability to conserve hair, clothing and leather items. The Bronze Age Egtved Girl, also discovered in Jutland, Denmark is a good example. Modern experimenters have been able to mimic bog conditions in the laboratory and successfully demonstrate the preservation process, albeit over shorter time frames than the 2,500 years the Haraldskær Woman's body has survived. Most of the bog bodies discovered had some aspects of decay or else were not properly conserved. When such specimens are exposed to the normal atmosphere they may rapidly begin to decompose. As a result, many specimens have been effectively destroyed.
Preserved bodies of humans and animals have been discovered in bogs in Britain, Ireland, northern Germany, the Netherlands, Denmark (both Jutland and Zealand), and southern Sweden. Records of such finds go back as far as the 18th century. The first bog body to be discovered was that of Kibbelgaarn body in the Netherlands, in 1791. It is not readily apparent at the time of discovery whether a body has been buried in a bog for years, decades, or centuries. However, during the 20th century, forensic and medical technologies (such as radiocarbon dating) were developed that allow researchers to more closely determine the age of the burial, the person's age at death, and other details. Scientists have been able to study their skin, reconstruct their appearance and even determine what their last meal was from their stomach contents. Their teeth also indicate their age at death and what type of food they ate throughout their life time.
However, in light of a recent National Geographic article, it may be possible that these injuries were not always inflicted by other people as a means of torture, but rather the weight of the bog. This would explain instances of smashed bones and the like.
The unity of the details of violent ritual slaughter over such a wide swathe of Northern Europe is a testament to a broadly unified culture, one which corroborates the breadth of material culture found in Celtic Iron Age archaeological sites of the La Tène type.
X-ray is a very important step in uncovering the bog bodies as it can draw a picture of a body in the peat, which can then be removed without harming it by cutting blindly. Radio carbon dating is also very common as it accurately gives the date of the find, most usually from the Stone Age. In terms of determining the cause of death of the bodies, in a surprising number of cases there are obvious signs of violence and murder. The Tollund Man, for example, had a rope knotted round his neck and Windeby I had been staked down under the water.
Because the peat marsh preserves soft internal tissue, the stomach contents can be analyzed. These give a good picture of the diet of those people. Facial reconstruction is one particularly impressive technique used in studying the bog bodies. Originally designed for identifying modern faces in crimes, this technique is a way of working out the facial features of a person by the shape of their skull. The face of one bog body, Yde Girl, was reconstructed in 1993 by professor Richard Neave of Manchester University using CT scans of her head. Yde Girl and her modern reconstruction are displayed at the Drents Museum in Assen. Such reconstructions have also been made of the heads of Lindow Man (British Museum, London, United Kingdom), and Windeby Girl (Archäologisches Landesmuseum, Schleswig, Germany).