Chapter 3 Natural Processes of Preservation

Preservation of Dead Bodies - Natural Mummification

• Human bodies pass through various stages of decomposition until skeletonized

• Rate of skeletonization - multiple environmental, biological, and cultural factors

• Interruption/delay in decomposition process of decomposition = mummification

• Mummification is the deviation in the natural cycle of decomposition

• Mummies more common in some environments vs others

• Important basic requirement of every natural modification environment - prevents/suppresses decomp

  • specifically, self-digestion of body tissues, bacterial decay, and fungal decay

• Body should be undisturbed and exposed to conditions of modification long enough

• If naturally mummified body subjected to change in environment - decay process resumes

  • ex: a change to a warm humid environment results in exposure of body preserved in glacial ice; one body thaws -so the process of decay resumes

• Realistically, no body preserves forever

Permafrost and Frozen Bodies

• Polar, high mountain, and permafrost - conducive to natural modification through ice

• Permafrost - term used for ground which is frozen year-round starting at a certain depth

  • found in Northern Canada, Alaska, Greenland, Eastern Siberia, Northern Russia, and Mongolia

  • in Russia, permafrost can reach over 1000 meters deep

  • Scandinavia - permafrost only 20 meters deep

  • also found in high mountain regions - frozen soil not deep

  • surface of permafrost soils may thaw during summer months (only a few meters deep)

• Two different types of natural modification

• Both operate on principle that all active processes involved in decomp stop with a large drop in temp below freezing point

Cold Mummification - Adipocere

• First type of mummification in ice - body’s fat is converted into adipocere or “grave wax”

• Only occurs in moist environment with little available oxygen

• Glacier bodies often preserved in this way

Cold Mummification - Dehydration

• Second type of ice or cold mummies - body in low temps and dehydrated

• Preserved due to soft tissue freeze-drying

• Water contained in a body directly and slowly extracted in a frozen/crystallized state

• With permafrost - ice also dried out the soil - leads to dehydration of cadaver in soil

  • ex: many well-known animal mummies from Siberian permafrost like a mammoth

• Degree of dryness through freezing varies based on immediate conditions of surrounding soil

• When temps fluctuate just above freezing point - ice mummies which aren’t completely dehydrated in all cell areas

  • moisture still in individual cells referred to as “moist mummies”

Bogs and Bog Bodies

• landscape features dating back end of Quaternary Ice Age (12,000 years ago)

• Excess of surface water - typically caused by high ground water levels, abundant precipitation, and poor drainage due to impermeable ground

• Standing excess water is oxygen deficient - leads to incomplete decomp of dead vegetation

• Hypoxia - is low oxygen levels that can inhibit the process of microbial decomp

• Dead plant material also subject to chemical changes

• Depending on climatic conditions and topography there are two principal types of bog:

Blanket Bogs

• Situated where ground and surface water accumulate

• In many cases - developed from stagnant lakes or in valleys

• Rich in nutrients - creates favorable conditions for plant and animal life

  • this content prevents preservation of soft body tissues

Raised Bogs

• Depend exclusively on water from precipitation and the nutrients it contains

• Referred to as ombrotrophic (rain fed) bogs

• Sufficient water from precipitation necessary for functioning

• able to bulge out and rise above groundwater level of their surroundings

• Contain harsh environmental conditions - create ecological system with limited # of species

• Only about 30 species of peat moss, some varieties of heather, and a few other plant species

  • Why? low in nutrients and oxygen and strongly acidic environments (pH levels 3.4-3.7)

• Water saturated peat under the cover of living vegetation - very poor for heat conduction - making raised bogs a cold environment

• Plants contributing most formation of peat are sphagnum mosses - absorbs nutrients entirely through their surfaces (no roots)

• Grow from tips of stems - lower stems die off at the bottom

• Dead plants transformed into peat - creates growing layer of insulation against underlying bedrock (preventing nutrients from enriching the bog)

Raised Bogs - Mummification

• The best conditions

• Not all raised bogs have the same specific characteristics

• Position of body in the bog - also play a role in whether it will be modified and to what extent

  • ex: some bog bodies, lower lying body parts better preserved than upper parts

• Peat mosses contain polysaccharides (compounds formed from sugar molecules) - such as sphagnum

• Sphagnum - stored in cell walls of peat mosses and slowly released as the plant sections die off so plays important role in preservation

  • transformed through several intermediate stages into brown humic acid

• Brown humic acid - bonds chemically with calcium and oxygen; inhibits growth of bacteria

  • also contains polyphenols (aromatic compounds, such as tannins or tannic acid)

• Polyphenols - bioactive substance in plants that can initiate tanning process

• Tanning process - preservative effect on the skin, hair, and even internal organs

• Tannins cause discoloration of soft tissues (copper-brown) and reddening of hair

• Muscle and fat tissues are not preserved

• A raised bog causes demineralization of bones (they often distort or disappear entirely)

• Third factor in preservation - oxygen-poor environment which suppresses putrefaction

• Cold water also slows decomp

Caves

• Two main types of caves:

  • Primary caves (e.g. lava caves) - formed at the same time as surrounding rock

  • Secondary caves (e.g. stalactite caves) - created after surrounding rocks, primarily limestone, have formed

• With environmental conditions, caves generally exhibit quite uniform parameters in its interior

• Temp and humidity are constant throughout the year

  • temp - corresponds to average yearly temp of the countryside location

  • ex: in Germany’s cave regions, about 48.2 degrees F, 98% humidity

  • humidity level depends on geographical location of the cave

• Caves in desert areas have very low humidity (e.g. American Southwest)

• Absolute darkness - bacterial breakdown of dead organisms in deep zones of caves proceeds very slowly

• Scavenging by animals reduced

• Natural mummification in caves is the most common in desert regions

• Soft tissue preservation - dehydration resulting from dry air

• Occurs in both cold and hot climates like Jordan and Siberia

• Natural mummification through air drying may also occur in humid caves (e.g. central Europe)

Deserts

• can be both cold and dry

• Dry, cold, or hot air and direct sunlight quickly release water from a dead body causing desiccation

• During dehydration process - decomp slows down/stops

• Surface of organism usually dries out first and hardens

• Depending on intensity and speed of dehydration - remaining moisture in some cases becomes trapped and leads to decay

• During desert mummification the preservation of inner organs varies

• In desert areas - mummification is also due to soil/sediment

• Hot desert sand can hasten the drying process

• Sand with high salt/sodium can increase likelihood of mummification

  • ex: predynastic mummies from Egypt have natural modification in hot sodium-rich desert sand

  • ex: Taklamakan desert mummies in Northwest China have desert climate and salt rich soil

• Natural mummies found in deserts are called “desert mummies” or “dry mummies”