5,000-year-old bones have revealed the oldest instances of mercury poisoning in history.
The poisoning was caused by exposure to cinnabar, a mineral that was pulverised and used in decorations, paintings and funeral rituals.
The research was carried out by a team from the University of Seville, which looked at 5,000-year-old bones from southern Spain and Portugal.
The study looked into the many and various interactions between people and mercury over the centuries.
It is the largest of its type to examine the presence of the substance in human bones.
A total of 14 specialists in biology, chemistry, physical anthropology and archeology participated and used as a sample the skeletal remains of 370 individuals from 50 tombs located in 23 archaeological sites in Spain and Portugal.
These bones span 5,000 years and date back to the Neolithic, Chalcolithic, Bronze Age and other periods.
The study found that the highest concentration of mercury exposure occurred at the beginning of the Chalcolithic, or copper, age, between 2900 and 2600 BC.
This timeframe coincided with the increase in the use of cinnabar, which is a vivid red mineral.
The research revealed that in tombs discovered in southern Portugal and Andalusia, thbpowder was used to paint megalithic chambers, decorate statuettes or stelae, and spread it over the dead in funerary rites.
This is similar to how red ochre was used to cover bodies by other ancient humans and, intriguingly, by Neanderthals too.
Just as in modern times those who worked with the building material asbestos, which is now known to be highly toxic, have suffered from mesothelioma – a type of cancer – so the Neolithic and other peoples could have accidentally inhaled, or ingested, the powdered cinnabar and became poisoned.
This led to high levels of deposits in their bodies.
The study recorded levels of up to 400 parts per million in the bones of some of these individuals.
Taking into account that, according to the World Health Organization, exposure to mercury, even in small amounts, can cause serious health problems, the bodies had a high level of intoxication.
As well as, as a by-product of working with the toxic mineral, the sheer scale of intoxication could also suggest a fascinating and disturbing alternative theory.
This is that the substance could have been voluntarily consumed by inhalation of vapours, or even eaten, because of the potent esoteric symbolism of the ruddy-hued rock.
From cinnabar’s red to the ancient Phoenician’s Tyrian purple, a dye fashioned by extracting secretions from thousands of sea snails, vivid colours have been revered and highly valued for centuries, even millennia.
This study’s findings provide a fascinating glimpse into the ritual behaviour of our distant ancestors, who simply would not have known how deadly their religious and cultural practices actually were.