So contrary to Rothammer (as discussed in u/Dondville) Marquet et al argue that the Chinchorros lead a less hierarchical lifestyle and that mummification isn't tied to status.

Mummification first started because of the pure heat of the environment. Natural mummification formed when bodies were left in dehydrated environments. This discovery of natural mummies is believed to be a primary inspiration for the creation of man-made mummies.

The earliest man made mummies were most often covered with black mud after the removal (and replacement with natural fibres) of inards and sectioning, then rejoining of the body.

The majority of early mummies were children, which lead Arriza to note a probable correlation between infant deaths and high arsenic levels in the local water (100 times the acceptable limit) and the EL Nino phenomenon. Mummification most likely started as a result of population rising (Marquet et al) and increased infant mortality. The common theory is that mummification was undertaken during periods of social stress caused by high infant mortality and a shortage of resources. Mummies were a tool to bring the community together, and perhaps played a religious, almost sacrificial role. Many of these mummies being children is probably those children who died from arsenic poisoning, which may have had importance.

It actually dissapeared for a while (or at least wasn't as popular) only to be replaced with a different type of mummification (red mummies as opposed to the older black ones). When similar birth/death rates occured. Red mummies were prepared slightly differently (different coloured mud, and incisions made to extract innards rather than dissection). Red mummies again seem to be a reaction to envrionmental pressures and have been interpreted again as sacrificial. The dying out of mummification can perhaps be seen as a sign of stability in the community and its resurfacing to be a sign of pressures returning.

#Sources:

Arriaza, B. (1995) ‘Chinchorro Bioarchaeology: Chronology and Mummy Seriation’ in Latin American Antiquity, Society for American Archaeology 6(1):35-55

Arriaza, B. (2005)’Arseniasis As An Envrionmental Hypothetical Explanation For the Origin of the Oldest Artifical Mummification Practice In the World/ Arsenicismo, Una Hipótesis Medioambiental Para Explicar El Origen De La Momicación Más Antigua Del Mundo’ in Chungara: Revista de Antropologia Chilena, Universidad de Tarapaca 3(2):255-260

Marquet, P., Santoro, C., Latorre, C., Standen, V., Abades, S., Rivadenira, M., Arriaza, B., Hochberg, M. (2012) ‘Emergence of Social Complexity Among Coastal Hunter-Gatherers in the Atacama Desert of Northern Chile’ in Proceedings of the National Academy of Sciences of the United States of America, National Academy of Sciences 109(37):14754-14760