Archaeologists have long puzzled over the artistically preserved bodies of nearly 200 ancient humans found along the Pacific coast of northern Chile and southern Peru. The bewigged and clay-covered remains, known as the Chinchorro mummies, resemble statues and date back 7000 years, making them the earliest artificially mummified bodies in the world. Later societies who practiced mummification tended to be politically and socially complex and reserved the privilege for adult elites. But the Chinchorro were different. They lived in a relatively simple society of fishers and seal and sea- lion hunters, and they started out mummifying young children. Why?
Research from an international team led by anthropologist Bernardo Arriaza of the University of Tarapaca in Arica, Chile, currently sheds new light on the Chinchorro people and supplies a possible explanation. By analyzing hair samples from 46 mummies from northern Chile, the team found that the Chinchorro ingested toxic levels of arsenic—a poison known to produce high rates of miscarriages and infant mortality—in their drinking water. Arriaza now theorizes that world’s oldest mummies were created by grief-stricken Chinchorro parents who suffered repeated losses of their children and who wanted to preserve their infants’ bodies and keep them above ground in shrinelike areas. This very early mummification practice, says Arriaza, “is an emotional response to an environmental contaminant.”
Excavators stumbled on the first Chinchorro mummies in Arica, Chile, in 1917, and subsequent studies by paleopathologists and physical anthropologists have revealed much about their preservation. The Chinchorro created their earliest mummies of children, including fetuses, by removing bacteria-ridden internal organs, packing body cavities with soil, strengthening limbs with sticks, coating the face with reddish-black clay, and adorning the head with a human-hair wig. Moreover, analysis has shown that they repeatedly repainted some of the clay masks to cover nicks and dents, strongly suggesting the mummies remained above ground, most likely in a shrine, for years after death. Eventually Chinchorro morticians extended the practice to adults, until they stopped making mummies in this distinctive style around 1700 B.C.
Arriaza began examining the possibility of arsenic poisoning among the Chinchorro in 2007, after reading about the toxic effects of this poison on human fetuses and infants. Arsenic occurs naturally in geological formations in many parts of the world, and as water weathers these strata, it carries the poison into local rivers. This hazard came to public attention in Chile in the 1960s, after the city of Antofagasta started drawing much of its water from a river that turned out to be laced with 860 micrograms of arsenic per liter— 86 times higher than World Health Association’s current provisional guideline. During the peak exposure from 1958 to 1965, infant mortality rates in Antofagasta soared by an estimated 18 to 24 %.
Arriaza suspected that the Chinchorro had suffered a similarly high infant mortality for exactly the same reason. The four earliest Chinchorro mummies—all children—came from the Camarones River Valley, where water tested as high as 1300 micrograms of arsenic per liter. So Arriaza collected hair samples from both Chinchorro and Pre-Inca mummies excavated from ten sites in northern Chile, whose water all tested above the WHO guidelines for arsenic, and then sent the samples to Dulasiri Amarasiriwardena, a chemist at Hampshire College in Amherst, for mass spectrometry testing. The mean arsenic values in hair from all ten sites pointed strongly to the chronic poisoning of the Chinchorro and other ancient peoples.
Many researchers may have assumed that environmental contamination was a major problem only for later industrial societies, but the new findings strongly suggest that this is far from true. “You can’t smell arsenic or taste it,” says Arriaza. “So the Chinchorro had no way of knowing they were being poisoned.”