It is not only the conditions present in the matrix, but climate affects the preservation of organic remains as well by dictating how much oxygen, warmth, and moisture are present. Caves are natural conservatories. Their chambers are protected from the elements and the soils and water inside them are often alkaline, which prevents the growth of bacteria, thus protecting whatever is inside them, including footprints! Tropical environments like those found in the Yucatan peninsula where the Maya lived, on the other hand, are typically highly destructive because of their heavy rains, acidic soils, warm temperatures, high humidity, erosion from weather, and abundant plant, animal, and insect activity. Additionally, the overgrowth common in jungles can quickly overwhelm sites, hiding them from outsiders (a good thing for overall preservation since it makes the sites hard for looters to find). The Temple of the Inscriptions at Palenque in Mexico (Figure 5.2.1), for example, was once brightly painted, but because of rain, humidity, and heat, the paint on the temple is no more. Temperate climates like those found in North America and Europe also are poor conditions for preservation because they are relatively warm but go through seasonal changes in temperature and moisture. One surprisingly good environment for preserving organic artifacts comes from natural disasters. The volcanic eruption of Mt. Vesuvius rapidly covered Pompeii, Greece in ash, and a violent wind storm at Skara Brae in Scotland (Figure 5.2.2) completely covered the site in sand. Both sites were exquisitely preserved. Rapid burial of sites through flooding, storms, and volcanic eruptions have preserved many of the world’s most impressive archaeological sites.
The materials from which archaeological remains were made also affect their preservation, or lack of it. Objects made of stone, clay, and metal are commonly found at archaeological sites. They are the most commonly preserved materials because they are inorganic and do not decompose, though they can weather, a process in which wind and water erode and wear away their surfaces. Stone tools dating back more than 2.5 million years have been found in archaeological sites and many are so well preserved that microscopic wear analysis can determine how the stones were used and even the dominant hand of the toolmaker. Baked clay and pottery can also survive most conditions as long as the items were adequately fired. However, highly acidic soils can damage the surfaces of baked clay items, and objects that were poorly fired or made from porous clay can become quite fragile in humid conditions. Metallic objects made with gold, silver, and lead can survive quite well, but objects made with copper, bronze, and other soft metals usually oxidize (rust) and can completely disintegrate, leaving only a green stain where they once rested. Underwater, metals at sites such as shipwrecks are preserved by the naturally occurring metallic salt in seawater that accumulates on their surfaces. In fact, these salts actually permeate metal objects, and it can be quite laborious to remove the encrustations.
CONDITIONS FOR PRESERVATION
King Tutankhamun's tomb is an excellent example of prime conditions for the preservation of material remains. First, his tomb remained undisturbed from 1323 BC until it was opened in 1922 by Howard Carter and his team. Although Carter believed there was some evidence that thieves had entered the tomb in antiquity (Treasures Removed from Luxor Tomb), the young pharaoh's tomb is known for the treasures, artwork, clothing, chariots, and multiple other artifacts that were buried with him. Second, the tomb had been sealed for over 3200 years keeping the conditions favorable for the preservation of the organic artifacts inside.
Figure \(\PageIndex{3}\): Howard Carter (kneeling), an Egyptian workman, and Arthur Callender at doors of burial shrines in Pharaoh Tutankhamen’s tomb. (1922).Figure \(\PageIndex{4}\):Tutankhamun receives flowers from Ankhesenamun. Image on the lid of a box found in King Tutankhamun's tomb.
Lack of Warmth
Figure \(\PageIndex{5}\): Leather shoe discovered in an ancient snowdrift. Dated between 1420 to 1260 BCE.
Extremely cold environments such as glaciers and year-round snowpack also provide optimal conditions for preservation. A bittersweet benefit of climate change is that many archaeological sites are being uncovered by the thawing of glaciers around the world. Examples of finds from such ice patch archaeology include atlatl(spear thrower) darts, baskets, clothing, and arrows still coated in paint and decorated with feathers. Other things that have been preserved in cold conditions include entire bodies of animals such as mammoths and even humans (Ötzi the ice man is perhaps the most famous example) that were frozen soon after their deaths and left unchanged until being recently uncovered.
ice patch
Accumulations of snow and ice at high elevations that do not completely melt during summer.
ice patch archaeology
Archaeological research that identifies and documents artifacts and organic materials left behind as the ice patches melt.
Another amazing ice discovery was made in 1993 on the Ukok Plateau of southern Siberia. Russian archaeologist, Natalya Polosmak excavated a burial chamber containing an ice-filled log coffin. After thawing the coffin, she found it contained the body of a young woman along with an elaborate headdress, clothing made of wool and silk, a wood-handled mirror, and colorful tattoos. Near the site, they also discovered six horses that appear to have been buried in order to accompany her to the afterlife. You can learn about "The Ice Maiden", as she has become known, by watching the Nova documentary Ice Mummies: Siberian Ice Maiden.
Lack of Oxygen
Oxygen is necessary for the microorganisms that cause decay to survive and reproduce so remains that were enveloped in sealed, airless environments—typically waterlogged conditions such as bogs—can be remarkably well-preserved. Bogs commonly produce oxygen-deprived anaerobic conditions. Examples of items that archaeologists have recovered from bogs include carts, wooden roads, and even ships such as ones from the 1800s and 1900s found in areas that were formerly part of San Francisco’s waterfront. One exceptional find is the nearly 50 “bog bodies” discovered at sites around the world, including the Windover bog body from Florida (researchers were able to identify his last meal) and Tollund Man from Denmark. These human remains are remarkably well-preserved thanks to conditions in the bogs. Their skin is darkened but is preserved, as are many internal organs, while their bones typically are not preserved.
anaerobic
Absence of oxygen.
Figure \(\PageIndex{6}\): The upper part of bog body discovered in Windeby, Germany.
Lack of Moisture
The extremely dry conditions typically found in deserts allow for the preservation of textiles, basketry, and other woven items. Entire Navajo hogans (homes) have been preserved in the American Southwest. Likewise, the dry conditions preserved the twine sandals, shown in Figure 5.2.7, which were worn by the Anasazi who lived in the cliff dwellings of Mesa Verde National Park in Colorado during the 12th century AD. Perhaps most remarkable is the natural mummification of bodies in places such as Egypt and Peru. Preservation can be so complete that Egyptian mummies retain their fingernails and hair and Incan mummies still have visible tattoos on their skin and retain the woven textiles in which their bodies were wrapped after death. However, it is not only mummies but other artifacts as well, as in the case of the Moche Lords of Sipán (Figure 5.2.8). The dry environment preserved their sepulchers, ceremonial regalia, jewelry, and scenes on pottery that provided information about the individuals' status in the culture.
Figure \(\PageIndex{7}\): Twine sandals from the 12th century AD.Figure \(\PageIndex{8}\): Reconstruction of the tomb of the Lord of Sipán in Huaca Rajada, Peru.
PRESERVATION AFTER RECOVERY
The problem with artifacts recovered from these three types of conditions is that artifacts remain well-preserved only as long as they’re kept in the conditions that allowed for their preservation. Once ancient wood is removed from waterlogged conditions, it splinters, cracks, and quickly begins to decompose. Likewise, once mummified bodies are exposed to normal (moist rather than dry) conditions, decomposition resumes. Once all three of the elements required for microorganisms to grow—heat, moisture, and oxygen—are restored, decomposition will occur and can actually be accelerated, sometimes quite dramatically. The terra cotta warriors in Xi’an, China, for example, had been preserved for more than 2,000 years in an enclosed chamber underground. Since being exposed in 1979, the 7,000 unique, brightly painted terra cotta warrior figures’ colors have faded, and the figures themselves have begun to disintegrate. Excavations at the site were halted until researchers could find a way to prevent further damage.
Figure \(\PageIndex{1}\): After being uncovered in 1979, the Terra Cotta Warriors in Xi'an, China, the brightly painted colors have faded.
REFERENCES
Treasures Removed from Luxor Tomb. (1922, December 28). The New York Times, 4.
Images
Figure 5.2.1 Temple of Inscriptions at Palenque, Chiapas, Mexico. (2010). By Strobilomyces under CC BY-SA 3.0 via Wikimedia Commons.
Figure 5.2.2 Skara Brae was built on the coast of Orkney. (2013). By Archaeology Scotland under CC BY-SA 4.0 via Wikimedia Commons.
Figure 5.2.3 Howard Carter (kneeling), an Egyptian workman, and Arthur Callender at doors of burial shrines in Pharaoh Tutankhamen’s tomb. By Harry Burton under Public Domain via Wikimedia Commons.
Figure 5.2.4 Tutankhamun receives flowers from Ankhesenamun. By Tiger cub under Public Domain via Wikimedia Commons.
Figure 5.2.5 Leather shoe discovered in the Jotunheimen Mountains in eastern Norway in 2006. By Vegard Vike/Kulturhistorisk museum under CC BY-SA 4.0 via Wikimedia Commons.
Figure 5.2.6 The upper part of bog body Windeby I a 16 year old boy on display at Archäologisches Landesmuseum Gottorf Castle, Schleswig Germany. C14 dated beween 41 and 118 AD. (2010). By Bullenwächter under CC BY-SA 3.0 via Wikimedia Commons.
Figure 5.2.7 Anasazi footwhere from Mesa Verde National Park. By inkknife_2000 under CC BY-SA 2.0 via Wikimedia Commons.
Figure 5.2.8 Reconstruction of the tomb of the Lord of Sipán in Huaca Rajada, Peru. By Bernard Gagnon under CC BY-SA 3.0 via Wikimedia Commons.
Figure 5.2.9 The Color of Terracotta Warriors. (2009). By Kevin Poh under CC BY 2.0 via flickr.
A derivative work from
"Digging into Archaeology:A Brief OER Introduction to Archaeology with Activities" by Amanda Wolcott Paskey and AnnMarie Beasley Cisneros, Faculty (Anthropology) at Cosumnes River College & American River College, ASCCC Open Educational Resources Initiative (OERI), 2020, under CC BY-NC 4.0.
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