Bog bodies are bodies, sometimes thousands of years old, that have been preserved from decay by the anoxic conditions of a peat bog and the humic acid in marsh water. These bodies are the most highly preserved window into people that lived in Iron Age Europe. The facial structures, skin, and internal organs of bog bodies are highly preserved, allowing close study, including what these people ate just before they died. Most of these bodies are from people that were killed violently, either as punishment for crimes or as a human sacrifice. The prevalence of human sacrifice in Iron Age Europe for successful crop yields and other reasons is well established.
The oldest bog body, Koelbjerg woman from Denmark, dates to roughly 8000 BC. This is so old that it predates the Bronze Age in Europe, instead being a rare artifact from Stone Age Europe. The most recent bodies date to the 16th century, including a woman from Ireland who was apparently buried in unhallowed ground (the bog) after a suicide. In some cases, the people were evidently killed violently, and feature multiple stab wounds. In one case, that of Tollund Man, one of the best preserved bog bodies there is, he was found buried with the rope around his neck that was used to kill him.
Bog bodies are typically recovered when people are harvesting the peat from bogs for fuel. Shortly after the body is revealed, it begins decaying, so quick preservation after that point is essential. Some bodies have badly deteriorated after their discovery due to improper preservation. Bog bodies generally have brown or black hair and skin, caused by chemicals in the bog that dye them. Archaeologists are fortunate to find any of these bodies, as the precise conditions conducive to their formation is rare, and generally occurs only in bogs near salt water. Because of this, one of the best locations in the world to find bog bodies is in Jutland, Denmark, which is frequently swept by winds bearing salty moisture.