On a warm spring day in 2019, researchers drilled into the earth beneath the streets of Cairo. Less than a kilometer away, the Great Pyramid of Giza shimmered on the horizon. About 4,600 years earlier, when workers were building the Great Pyramid, the current excavation site lay on the sandy bottom of the port of Khufu.
In this ancient port – the oldest known port in the world – researchers have identified the first major case of man-made metal contamination. Although the Giza Necropolis is famous for its pyramids and shriveled mummies, a new study published in geology provides unprecedented evidence of a largely overlooked aspect of ancient Egyptian civilization: persistent metalworking over centuries.
“The sediments are as important as monuments.”
The discovery sheds light on life beyond the pharaonic and princely elites of ancient Egypt, researchers said. “We want to know more about 95% of people, not just the elite,” said Alain Véron, a geochemist at France’s Aix-Marseille University. His views echo those of Christophe Morhange, a geoarchaeologist at the same institution, who underlined the importance of the sedimentary record in reconstructing historical narratives.
“The sediments are as important as monuments,” said Morhange, emphasizing the often overlooked importance of the soil beneath our feet.
A surprising story of contamination
The researchers used geochemical tracers to study metalworking activities around the ancient port of Khufu. The port, on a now-defunct branch of the Nile near the Giza Plateau, was essential for transporting materials and was the site of a significant copper tool industry. These tools, some of which workers alloyed with arsenic for durability, included blades, chisels and drills used to work materials such as limestone, wood and textiles. The researchers used inductively coupled plasma mass spectrometry (ICP-MS) to measure levels of copper and arsenic, as well as those of aluminum, iron and titanium, and created a chronological framework using six carbon-14 dates.
The study traced the beginning of metal contamination to around 3265 BC, earlier than researchers expected. Contamination during this predynastic period suggests that human settlement and metalworking at Giza began more than 200 years earlier than previously documented.
“You only find what you are looking for.”
Although researchers have found direct evidence of a predynastic civilization in only 13 tombs north of Giza, Morhange believes the geoarchaeological finds provide further clues. Because researchers focused so heavily on the pyramids and other tombs, they may have missed evidence of earlier occupation at the site, he explained.
“You only find what you are looking for,” he said.
The researchers found that metal contamination peaked during the late pyramid-building period around 2500 BC and continued until about 1000 BC. “We have found the oldest regional metal contamination ever recorded in the world,” Véron said. Copper levels during this period were “five to six times higher than the natural background,” he continued, suggesting significant local industrial activity.
Andrew Shortland, an archaeologist at Cranfield University in the UK who was not involved in the study, raised concerns about the proposed time frame. “I don’t think six dates is enough,” he said, referring to the number of carbon-14 dates used.
Nevertheless, Shortland acknowledged the study’s broader conclusions regarding man-made metal contamination at Giza.
Adaptation to environmental stress
The study provided further insight into how ancient Egyptians adapted to environmental challenges. As the Nile receded and the port of Cheops shrank, metalworking continued. When the Nile reached its lowest level around 2200 BC – a period marked by social unrest and grim rumors of cannibalism – metal contamination remained high, suggesting a robust infrastructure and workforce.
Véron explained that the Nile’s retreat initially presented opportunities for local communities. Previous palynological research – the study of pollen grains – has shown that agricultural activity increased as the receding Nile revealed fertile floodplains. Even when construction of the pyramids at Giza ceased, metalworking probably continued to support burgeoning agricultural activities.
Dominik Weiss, a geochemist at Imperial College London, found the study “extraordinarily well done and carefully conducted”. He pointed to the attraction of high-profile sites such as the Giza Necropolis and praised the new connection between geochemistry and history and the opportunity to shed light on the everyday lives of ancient Egyptians.
“The chemical imprint of human activities remains and cannot be erased,” said Véron.
—Evan Howell, science writer
Quote: Howell, E. (2024) 5,000-year-old copper pollution found near the pyramids, Eoss, 105, https://doi.org/10.1029/2024EO240382. Published on 23 August 2024.
Text © 2024. The authors. CC BY-NC-ND 3.0
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