Chinchorro mummies

Chronology

Scientific study has shown that Chinchorro mortuary practices developed over more than 5,000 years. The earliest known naturally preserved individual associated with the culture, known as Acha Man, died around 7020 BCE. His body was preserved by the hyper-arid conditions of the Atacama Desert.

By about 5050 BCE, the Chinchorro had begun preserving their dead through artificial mummification. The earliest known example is a child buried in the Camarones Valley, about 60 kilometres (37 mi) south of Arica, in what is now northern Chile. Artificial mummification continued for about 3,000 years before ending around 1800 BCE.

Archaeologists recognise several forms of Chinchorro mummification, including black, red, mud-coated and bandage mummies. Although these forms are associated with different periods, their dates overlap, and more than one technique has been found within the same cemetery. The evidence therefore does not support a simple sequence in which one method completely replaced another.

Imaging and genetic studies

The Chinchorro mummies have been examined using imaging and genetic techniques intended to limit damage to the fragile remains. In 2016, 15 mummies, including adults, children and infants, underwent computed tomography (CT) scanning. The scans allowed researchers to examine the bodies without opening them.

Thousands of cross-sectional images showed the internal structure of the mummies, including wooden supports, packing materials and surviving soft tissue. Researchers planned to use the images for virtual dissections and digital reconstructions of the individuals' muscles and facial features. The scans also showed that one small object previously believed to be a mummy did not contain a human skeleton and was instead a figurine.

Small samples of skin and hair were also collected for planned genetic testing. Separate DNA studies have identified individuals from the Chinchorro culture as belonging to mitochondrial haplogroup A2.

Diet and health

Scientists have studied Chinchorro remains to reconstruct aspects of their diet, health and living conditions. Chemical analysis found that most of their food came from the sea, supplemented by land animals and plants gathered near river mouths. The findings support other archaeological evidence that the Chinchorro depended heavily on the Pacific coast for food.

Preserved hair has been used to study exposure to arsenic, a toxic substance that occurs naturally in drinking water in northern Chile. In a 2010 study, researchers tested 46 hair samples from five burial sites, including Chinchorro remains from Morro, Yungay and the Camarones Valley. Samples from Morro and Camarones, as well as from Iquique, had arsenic concentrations above 10 micrograms per gram. The Camarones Valley is about 100 kilometres (62 mi) south of Arica.

Researchers have also found evidence of head lice in preserved Chinchorro hair. They examined a 2 cm × 2 cm (0.79 in × 0.79 in) area of scalp on each of 63 mummies from the Arica-Camarones coast dating from about 5000 to 3000 years ago. Fifty of the 63 mummies, or about 79 percent, had lice or their eggs. The researchers suggested that the frequency of lice could help investigate how closely people lived together and how settled Chinchorro communities were.

Modern conservation

After surviving for about 7,000 years in the extremely dry Atacama Desert, some Chinchorro mummies have begun to deteriorate under modern storage conditions. A 2016 study reported increasingly rapid damage during the previous decade among mummies held at the University of Tarapacá in Arica, northern Chile. Areas of preserved skin had darkened and begun to ooze.

Researchers from Harvard University and the University of Tarapacá found bacteria and fungi on the damaged skin, including microorganisms capable of breaking down collagen and keratin, important proteins in human skin. Experiments showed that deterioration increased sharply at 75–80 percent relative humidity. After 21 days, mummy skin kept at this humidity showed increased collagen breakdown. The researchers recommended keeping museum collections at about 40–60 percent relative humidity, since very dry conditions can also damage the remains.

Conservation is more difficult for Chinchorro remains still buried in the Atacama Desert. Some lie close to the surface and may be exposed by construction, erosion or other disturbances. Unlike museum collections, archaeological sites cannot be kept at controlled temperature and humidity, leaving unexcavated remains vulnerable to environmental changes that increase moisture.

Bandage technique

The bandage technique is a rare form of Chinchorro mummification known from three infants. The body was skinned and strengthened with sticks, then wrapped in strips of human or animal skin about 2 cm (0.79 in) wide. The head and face were prepared in the same way as those of red mummies, and the body was painted red.

The three infants have not been directly radiocarbon dated. Based on the way the bodies were prepared, they are thought to have been contemporary with the red mummies. An adult mummy with similar bandaging limited to the legs has also been documented.

Black mummy technique

The black mummy technique was used from about 5000 to 2800 BCE and is the oldest of the main Chinchorro artificial mummification methods. The earliest examples are known from the Camarones area on the Pacific coast of northern Chile, where the technique was in use by about 5000 BCE. Later black mummies have been found at several sites around Arica, where the method became more elaborate.

Preparing a black mummy involved taking the body apart and rebuilding it. The skin was removed, followed by the soft tissue and internal organs, and the skeleton was disassembled. The bones were cleaned and returned to their correct positions. They then strengthened the reconstructed skeleton from the head to the ankles with thin wooden poles, tied in place with reed cords. The inside of the body was filled with materials including grasses. A layer of grey clay about 2 to 4 cm (0.79 to 1.57 in) thick, depending on the part of the body, covered the bones, wooden supports and cords and was used to restore the body's shape.

Once the body had been rebuilt, surviving human skin was placed over it. Seal or sea lion skin could be used where the person's own skin was missing. The face and other features were modelled, and a short wig made from human hair was attached to the head. Finally, the reconstructed body was covered with a thin layer of black manganese dioxide-based paint, while the wig was left unpainted. This dark coating gives black mummies their name.

Mud coat technique

The final style of Chinchorro mummification was the mud-coat (3000-1300 BCE). Ecologically speaking, at the time of the Chinchorro culture the region was relatively stable. It has been suggested by environmentalists that the incredible preservation of these mummies is also influenced by the pedogenic (the evolution of soil) creation of clays and gypsum, which act as cementing agents, and the latter as a natural desiccant. The malleable clay allowed for the morticians to mold and create the colorful appearances of mummies, with the added bonus of the fact that the foul smell of the desiccating mummy would be covered. Artisans no longer removed the organs of the dead; instead a thick coat of mud, sand and a binder like egg or fish glue was used to cover the bodies. Once completed the mummies were cemented into their graves. The change in style may have come from exposure to outsiders and their different cultures, or from the association of disease with the rotting corpses.

Red mummy technique

The red mummy technique is dated to about 2570 to 2090 BCE and has been found at sites along the coast of northern Chile, including Arica, Camarones, Punta Pichalo, Bajo Molle and Patillos. Unlike the black mummy technique, the body was not completely taken apart. Instead, incisions were made at several points on the body, including the shoulders and groin, to remove the internal organs and some of the muscles. The head was removed so that the brain could be extracted, and the body cavities were dried with glowing coals and ashes.

Thin wooden poles were inserted beneath the skin through the arms, legs and along the spine to strengthen the body. The empty cavities and head were then packed with materials including seabird feathers, soil and camelid fibre to restore the body's shape. The incisions were sewn closed with human hair or reed fibres.

The head was reattached and fitted with an elaborate wig made from human hair, sometimes reaching about 60 cm (24 in) in length. The wig was held in place with a black manganese paste, and the facial features were modelled. Finally, the body was covered with red ochre, while the face was generally left black.

Natural mummification

Of the 282 Chinchorro mummies found to date, 29% of them were results of the natural mummification process (7020–1300 BCE). In northern Chile, environmental conditions greatly favor natural mummification. The soil is very rich in nitrates which, when combined with other factors such as the aridity of the Atacama Desert, ensure organic preservation. Salts halt bacterial growth; the hot, dry conditions facilitate rapid desiccation, evaporating all bodily fluids of the corpses. Soft tissues, as a result, dry before they decay and a naturally preserved mummy is left. Even though the Chinchorro people did not mummify the bodies artificially, the bodies were still buried wrapped in reeds with grave goods.