Bog Chemistry & Archaeology
Peat bogs are wetlands formed in areas which lack drainage and as a result, they are characterized by anaerobic conditions. The unique physical and biochemical composition of northern European peat bogs provide an excellent environment for the natural preservation of organic and otherwise perishable materials (human bodies, clothing, wood, etc). These bogs accumulate large quantities of dead plant matter, usually mosses that keep adding up layer after layer, forming peat.
When the dead plant matter decays, it releases acids that have pH levels similar to vinegar, conserving organic materials by basically “pickling” them. The combination of these key factors (i.e. highly acidic water and a lack of oxygen) with the overall cold temperature of the water (usually below 4 °C) allowed for a great wealth of archaeological material to survive for thousands of years. As such, peat bogs in northern Europe are veritable repositories of artifacts from ages past.
Among the most interesting items recovered from peat bogs, aside from the famous mummies collectively known as bog bodies, is something called bog butter; perhaps not the most creative term, but rather self-explanatory, the term bog butter simply refers to butter that was buried within a bog. The butter was usually placed within a container – a wooden tub, a bucket or a keg – or wrapped in leather or tree bark before being buried. In some cases willow baskets, textiles, animal skins, bladders or intestines were used instead.
The practice of “making” bog butter appears to have been widespread among the Irish who later introduced it to Scotland, probably when they migrated to the region approximately 1700 years ago and became the Scots. Bog butter burial dates back to the Iron Age (400 BC and beyond) in Ireland, while in Scotland the oldest evidence dates back to the 3rd century AD. However, the practice became most common during medieval times (11th – 14th centuries), especially in Ireland. Almost 300 deposits of incredibly well-preserved bog butter were discovered in Ireland and Scotland since 1817, most of them by local workers who cut the peat to use it as fuel.
Peat Bogs as Natural Refrigerators
Despite the centuries of continuity, the practice was abandoned around the 19th century, after which it was all but forgotten. No one knows for certain why butter was ever buried in bogsand there are numerous theories concerning the origin and purpose(s) of this practice. For example, one theory proposes that peat bogs were used as “refrigerators” by the Ancient and Medieval Irish and Scots. The naturally cold environment with its anaerobic and antiseptic conditions made northern peat bogs excellent places to store and preserve certain foods.
Dairy products were fairly common among the Irish: milk, curds, cheese and butter were staples of Irish cuisine since ancient times. Milk, however, was only generally available during spring and summer, so cheese and butter, which kept longer, were made. Butter was a very significant foodstuff in Ireland (and all of northern Europe) because of its high fat content. In a world where a balanced diet was not readily available, butter provided a great source of nutrition. The dairy product was, in many ways, the northern equivalent of olive oil, the Mediterranean staple.
That is why it was important for the Irish (and the Scots) to find a way of preserving butter and make it available year-round. Innovative as they proved to be, these people came up with a simple and natural solution to the problem – they buried lumps of butter in the local bogs, successfully exploiting the biochemical properties of their surrounding environment. This practice might have developed as an alternative to salting the butter, since salt was not always available or affordable. Interestingly enough, none of the recovered batches of bog butter contain any salt.
The low and sometimes freezing temperatures slowed degradation, while the lack of oxygen combined with the acidic conditions of the bog prevented microbial growth and oxidation. Thus, bog butter could have been stored simply for preservation, to avoid it from spoiling, especially during the warm spring and summer months. If this was the case, most of it was eventually recovered for consumption. The batches that have been (and still are) discovered in modern times were simply misplaced, lost or forgotten by those who buried them there. Or perhaps the owners died before getting to recover their delicious bog butter.
Bog Butter – a Delicacy?
Another similarly pragmatic theory offers a more gastronomic-oriented perspective: bog butter might have been buried to alter its taste and produce strong and specific flavors. Bog butter, although invariably lacking salt, was sometimes mixed with other substances, such as honey, beeswax and garlic. Numerous and various accounts allude to bog butter and mention it in a gastronomic context, supporting this theory. For example, Sir William Petty, an English economist, physician, scientist and Cromwell supporter who spent 20 years in Ireland, described the food of the Irish in his 1672 Political Anatomy of Ireland, mentioning “eggs and butter made very rancid, by keeping in bogs.”
An anonymous Irish poem titled Hesperi-neso-graphia (first published in 1712 but written between 1660 and 1680) describes Ireland the “Western Isle renow’d for bogs”:
[And] where in bowels of the ground
There are great heaps of butter found,
Of which, with blood of living beast,
The natives make a dainty feast;
Bog butter is further alluded to in the poem:
But let his faith be good or bad,
He in his house great plenty had
Of burnt oat-bread, and butter found,
With garlick mixt, in boggy ground;
So strong, a dog with help of wind,
By scenting out, with ease might find.
And this they count the bravest meat
That hungry mortals e’er did eat.
Meanwhile, the Irish Hubridas, a poem from the same cycle as Hesperi-neso-graphia, notes a culinary practice of the Irish peasants:
Butter to eat with their hog,
Was seven years buried in a bog.
Thomas Dingley (or Dineley), an English antiquary who visited Ireland in 1680, wrote about “butter, layed up on wicker baskets mixed with a sort of garlic and buried for some time in a bog to make provision for a high taste in Lent” when describing Irish traditional cuisine. Sir William Robert Wills Wilde (father of Oscar Wilde) presented a paper to the Irish Natural History Society in 1856 in which he made some observations concerning bog butter:
Why or wherefore the people put their butter in bogs I cannot tell, but it is a fact that great quantities of this substance have been found in the bogs, and that it has invariably assumed the physical and chemical characters presented by the specimen now before the Academy. It is converted into a hard, yellowish-white substance, like old Stilton cheese, and in taste resembling Spermaceti; (…) Two questions arise, at what time the Irish ceased to bury butter, and how long it would take to produce this change in it.
So it is possible that bog butter was, at least in Ireland, a delicacy. Burying perishable foods in order to preserve them was a form of primitive food processing and such practices were found all over the world. To give a few examples, Inuit kiviak (auks fermented in seal skin) and igunaq (fermented walrus steaks), Chinese century eggs and Icelandic kæstur hákarl (fermented shark) are all prepared similarly to bog butter – burial was (and is) a necessary step in their preparation.
Century eggs, also called millennium eggs, are said to have been “discovered” some 600 years ago in Ming China when a peasant found some duck eggs buried in clay and slaked lime (calcium hydroxide) in his backyard. The eggs had been there for a couple of months, from when he used the material to construct his house. Curious, the man tasted the eggs, which had turned black, and liked the taste so much that he started making his own, adding salt and other spices.
Century eggs generally taste like sharp cheese, just like bog butter, which has been likened to old Stilton cheese. But the similarities might not stop there: there is a chance that bog butter – as a delicacy –came into being when someone discovered a previously buried stash of butter in a bog. Upon presumably tasting the substance and enjoying its taste, the person would have decided to bury his own butter and enhance its taste by adding various ingredients (such as wild garlic). A likely scenario, in which butter ceased to be buried for preservation reasons alone, the practice developing into a refined gastronomic procedure.
Another very similar food was rue tallow in the Faroe Islands. Rue tallow is rendered sheep fat and it was mainly used for making candles and soap. The Faroese, however, ate it. Danish priest and topographer Lucas Jacobsøn Debes who moved to the Faroe Islands in 1652 and wrote the first book about the Faroes (published 1673) described how rue tallow was prepared:
It is there [in the Faroes] called “preserved tallow” and “rue tallow” and was thus treated: the tallow, principally obtained from sheep, was cut in pieces, and allowed to rot awhile; it was then rendered, and cast into large pieces, which they dig and put in moist earth to keep it, it growing the better the longer it is kept, and when it is old and is cut, it tasteth like old cheese. The most able peasants have ever much endeavored to bring together a great quantity of that tallow, so that a countryman had sometimes in the tallow dike (that is, a place-in the earth where it is kept) above 100 loads, and this hath always been looked upon as the greatest riches of [the] Faroes. For when sheep die, such tallow is very necessary in the land, the longer it is kept being so much the better; and foreign pirates having little desire to rob it from them. It may, therefore, not unreasonably be termed a hidden treasure, which rust doth not consume, nor thieves steal away.
Bog butter could have been treated very similarly in Ireland. It could have also been buried – at least in some instances – to protect it from thieves, just like rue tallow in the Faroe Islands. Ireland, like its neighbor Britain, has had its fair share of foreign invasions. The Vikings, for example, raided the island for over two centuries (between 795 and 1014 AD). To avoid having their possessions taken, food supplies included, the Irish locals hid them in various places, including bogs. But bog butter stashes date back to more than a thousand years before the first Viking incursions in Ireland.
While it is almost certain that butter caches were buried in order to be preserved and sometimes hidden from marauders, the origins of bog butter lie in the Iron Age and the original purpose behind the practice is not so pragmatic. The oldest hoards of bog butter were discovered in geographical locations of great ritual significance to the ancient, pagan Irish, alongside tribal boundary areas. For example, a 10 kg chunk of bog butter discovered in County Meath was buried in a boundary area where three ancient tribal boundaries met more than 2000 years ago.
Similar Iron Age bog butter finds have been made in other Irish counties, always alongside important tribal boundaries. A wide array of Iron Age artifacts associated with religious rituals, including human sacrifice, were also found in conjecture with bog butter. These finds can be arranged in several categories: weapons (swords, spears, shields), items associated with horse-riding and equestrian procession (harness pieces, bridle bits, wooden yokes), jewelry (gold collars, fibulae, bracelets, etc), regalia pieces (horned head-dresses, cloaks), objects associated with feasting (drinking cups, cauldrons, bowls, etc), boundary markers (anthropomorphic wooden sculptures), tools (axes, sickles, etc) and bog bodies.
These items were ritually deposited in the waters and bogs alongside tribal boundary areas as votive offerings to regional deities and are interpreted as serving a protective function. One hypothesis connects the phenomenon with kingship rituals, with the inauguration of a new tribal chieftain or king. As such, the new ruler rode (sometimes in a chariot) in procession to the borderland of his realm, the place of his inauguration. There, a great feast was held, after which other rituals followed. In some cases, human sacrifice occurred, although the details are murky.
The most famous bog bodies discovered in Ireland, the Old Croghan Man (County Ofally), Clonycavan Man (County Meath) and Gallagh Man (County Galway) were all sacrificed and deposited in a bog nearby a hill associated with kingship initiation rituals. All these men were in their 20s when they were killed and all of them are believed to have been of high social status. It is possible that they were [local] kings/chieftains whose reigns coincided with bad weather and therefore poor yields of milk and cereals, and that they were sacrificed to fertility deities to ensure better harvests.
Whether they were murdered before, after or during the inauguration of a new ruler is unknown, but the latter seems the most plausible. Their last meals, which were of great symbolic meaning, consisted of cereals and buttermilk, highlighting the importance of these substances. In the Iron Age, the main purpose of a (tribal) king was to ensure the fertility of his land –his reign had to bring good weather and, consequently, good harvests and good yields of milk.
Failure to do so brought death in ritual form, probably to appease whatever gods presided over the aspects of fertility. This form of human sacrifice was part of a wider northern European tradition which predates the Iron Age and persisted until the 11th century in places like Scandinavia. In any case, these failed rulers were laid to rest at sacred sites associated with kingship initiation rituals, alongside tribal boundaries. Various objects, including butter, were deposited next to them as part of the aforementioned inauguration ritual.
This rite of kingship initiation appears to have been a hierogamy, a sacred wedding between the ascending king and his land which represented a goddess (i.e. the earth goddess/goddess of fertility). This not only consecrated the new ruler, giving him divine prerogatives, but also ensured the fertility of the realm and the well-being of his people whose survived relied on plentiful harvest and yields of milk. Therefore, the ritual feast was the new king’s wedding feast, an integral and central part of the kingship inauguration ceremony.
After the feast, the ascending king “shared” some of his possessions, his horse harness, his weapons and his initiation regalia with his “wife” by burying them on his realm’s borderlands; it is possible that his horse was sacrificed and eaten by those present at the ceremony. Other items, such as boundary markers, agricultural tools and butter, were placed in the bog as votive offerings. All this had the role to consecrate the new king and his new authority. These kingship rituals survived into the early Christian era of Ireland, but in a mutated form: the inaugurated king gave his horse, his harness, weapons and attire to his retainers instead of throwing them in a bog.
It was in this ritual context (of kingship inauguration ceremonies) that butter was first buried in a peat bog as a votive offering, never meant to be recovered. The origins of bog butter are, therefore, purely ritual in nature. This also means that bog butter is a by-product of pagan religious practices from the Iron Age, the original motivation for burying butter being ritualistic. Over time, this motivation (and practice) became secularized.
Perhaps a lump of butter (buried in ritual context) was discovered in a bog by chance by someone who passed by. This unknown person from an unknown time inspected the substance and tasted it out of curiosity, discovering that it was still edible and might have even enjoyed the taste of bog butter, deciding to make more; the technique was very simple after all. The person also realized that butter could be preserved and stashed for leaner times in the bog, and started doing just that.
With bog butter being made for more utilitarian reasons – that is, preservation – the foodstuff became available to more people year-round, not just in spring and summer. Those with more sophisticated palates started to experiment, giving new gastronomic dimensions to bog butter. They added honey, garlic and various spices to enhance certain flavors and create new, stronger tastes. The result was a delicacy akin to other foods processed through burial (kiviak, century eggs, hákarl, etc).
In some cases, people might have buried their butter for other, non-culinary reasons, such as hiding it from marauders and thieves (e.g. the Viking invasions and other conflicts from the Middle Ages). Motivations, reasons and partly the methods changed over time. The batches of bog butter that were unearthed in the past 200 years span from the Iron Age to the modern era. Some of them were buried as votive offerings not meant to be recovered, while others were simply forgotten, misplaced or lost, or whoever buried them died.
By the 19th century, bog butter stopped being made; it was a sudden end to a practice which endured for more than 2,000 years in Ireland. Around the same time, historians and scholars took a keen interest in the bizarre foodstuff, but much to their frustration, they could not find anyone in Ireland able to know or remember why and how bog butter was made, or why it stopped being produced. Even today, there are multiple theories proposing different origins and motivations for bog butter. These theories are not mutually exclusive and, if anything, they complete each other as we have seen in this article.
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