Metal used by craftspeople at the pre-Inca site of Castillo de Huarmey in Peru may have travelled hundreds of kilometres from present-day Bolivia, according to new archaeological research.Image Credit : M.Giersz
The evidence comes from a small fragment of metallurgical waste discovered in the burial of a young metalworker at the important Wari archaeological site on Peru’s northern coast.
Chemical, mineralogical and lead-isotope analyses suggest that the material most likely originated around Pulacayo in modern Bolivia before being transported across the Andes.
The discovery provides another indication that economic and technological connections stretched across the Andes centuries before the rise of the Inca Empire.
A Metallurgist’s Grave
Castillo de Huarmey was an important Wari necropolis more than 1,300 years ago.
The Wari developed an extensive network of administrative and ceremonial centres and roads long before the emergence of the Inca Empire.
In 2012, an international archaeological team led by Polish researchers discovered the first intact royal Wari tomb at Castillo de Huarmey. Later excavations revealed burials associated with specialised craftspeople.
Among them was a burial belonging to a man estimated to have been about 20 years old.
More than a dozen bronze objects accompanied him, including a metal saw, axe, knives and chisels.
Researchers also discovered a small dark fragment in his hand.
The material initially appeared insignificant, but analysis identified it as speiss or matte, a by-product produced during the smelting of metal ores.
That tiny fragment became the key to investigating the geographical origin of the metalworking material.
A Geological Fingerprint
Researchers analysed the fragment using lead isotope analysis.
Lead isotope ratios vary naturally between different geological deposits. This allows scientists to compare archaeological metal or metallurgical residues with geological samples and identify potential source regions.
The researchers compared the Castillo de Huarmey sample with ores, rocks and metal artefacts from Peru, Bolivia, Chile, Argentina and other parts of the Andes.
Several possible sources initially emerged, including deposits in southern Peru and Bolivia.
When the isotope results were combined with chemical and mineralogical evidence, however, the Pulacayo region of Bolivia emerged as the most likely source.
Previous analysis of other metal objects from Castillo de Huarmey has also indicated connections with the same region.
Pulacayo and Ancient Metal Networks
Pulacayo later became one of South America's major mining areas, particularly because of its silver resources.
Copper was also extracted there during pre-Inca periods.
The research suggests that material associated with metal production travelled from the Bolivian region towards Castillo de Huarmey, demonstrating that communities separated by hundreds of kilometres were connected through the movement of valuable materials.
The evidence does not establish exactly how the material travelled or identify a single trade route.
However, researchers propose that communities probably processed ore close to its source before transporting it north.
Metal May Have Travelled as Semi-Processed Material
Transporting large quantities of ore over long distances would have been inefficient because ore can contain relatively small quantities of usable metal.
Researchers therefore suggest that ancient communities may have processed material near the mining areas before moving it across the Andes.
Metal could have reached Castillo de Huarmey as partially processed material, semi-finished products or completed objects that were later melted down and reused.
The researchers suggest that llama caravans may have transported some of these materials through the Andes. They also note that some shipments could have travelled by maritime routes.
The exact routes remain uncertain.
Technology May Have Travelled With the Metal
The movement of metal may have involved more than the exchange of raw materials.
Researchers suggest that technological knowledge and specialist expertise could have circulated through the same networks.
Metallurgical techniques require specialised knowledge, and long-distance connections may therefore have helped transfer skills as well as materials.
The young man's burial provides an unusual window into this technological world.
His grave contained numerous metalworking tools, including a saw, axe, knives and chisels, identifying him as a specialist craftsperson.
The speiss or matte fragment placed in his hand may have had a particular professional significance.
Researchers suggest that it could have functioned as a technological reference sample, a quality benchmark, or a symbol representing the deceased man's profession and status.
Its exact meaning remains unknown.
What the Evidence Does — and Does Not — Prove
The isotope evidence provides a strong indication of a geographical connection between Castillo de Huarmey and the Pulacayo region.
However, the archaeological evidence does not currently establish that primary smelting took place at Castillo de Huarmey.
Researchers have not found smelting furnaces or large concentrations of metallurgical waste at the site.
This distinction is important.
The presence of a metallurgical by-product and specialised tools demonstrates a connection with metalworking, but it does not by itself prove that raw ore was smelted at Castillo de Huarmey.
The available evidence instead supports a broader interpretation involving the movement of metal or processed metallurgical materials across the Andes.
Why This Discovery Matters
The discovery provides evidence for long-distance economic connections in the Andes centuries before the Inca Empire.
A tiny fragment from a burial has helped researchers trace a possible link between northern coastal Peru and a mining region in modern Bolivia.
The finding also demonstrates how specialised craft production could be embedded within wider exchange networks.
The objects buried with the young metalworker show that metallurgical knowledge was valued and that metalworking was a specialised occupation.
Meanwhile, the geological signature of the metallurgical waste suggests that the materials used by such craftspeople could originate hundreds of kilometres away.
Together, these lines of evidence reveal an interconnected Andean world in which materials, finished objects and potentially technological knowledge moved across considerable distances.
What’s Next?
Further archaeological and metallurgical research could help determine how widespread these long-distance connections were.
Comparing additional metal objects and metallurgical residues from Castillo de Huarmey with geological sources across the Andes may reveal whether the Pulacayo connection was an isolated occurrence or part of a sustained exchange network.
Future excavations could also clarify whether metalworking at Castillo de Huarmey involved imported semi-processed materials, recycling of finished objects, or other forms of production.
At present, the absence of furnaces and large metallurgical waste deposits prevents researchers from confirming primary smelting at the site.
Conclusion
A small fragment held in the hand of a young metalworker buried at Castillo de Huarmey has provided an unexpected clue to the scale of pre-Inca trade.
Lead isotope, chemical and mineralogical evidence points towards the Pulacayo region of present-day Bolivia as the most likely source of the material.
The finding suggests that metals or semi-processed metallurgical materials could travel hundreds of kilometres across the Andes before reaching craftspeople on Peru's northern coast.
The evidence also raises the possibility that metallurgical knowledge travelled alongside these materials.
More than 1,300 years ago, long before the rise of the Inca Empire, communities across the Andes were already participating in complex economic and technological networks.
FAQ
Where was the metalworker buried?
The burial was discovered at Castillo de Huarmey, an important Wari archaeological site on Peru's northern coast.
How old is the burial?
The site was an important Wari necropolis more than 1,300 years ago. The young man buried there was approximately 20 years old.
What was found in the grave?
The burial contained more than a dozen bronze objects, including a metal saw, axe, knives and chisels, as well as a small fragment of speiss or matte.
Where did the metalworking material come from?
Chemical, mineralogical and lead-isotope evidence indicates that the material most likely originated around Pulacayo in modern Bolivia.
How was its origin identified?
Researchers compared lead isotope signatures and other chemical and mineralogical characteristics with geological and archaeological samples from across the Andes.
How did the metal travel?
The exact route is unknown. Researchers suggest that some materials may have travelled through the Andes in llama caravans, while other shipments may have used maritime routes.
Does the discovery prove that metal was smelted at Castillo de Huarmey?
No. Researchers have not found smelting furnaces or large concentrations of metallurgical waste at the site, so there is currently no definitive evidence that primary smelting occurred there.
