A significant archaeological discovery has been made in southern Africa, revealing the oldest known mine, estimated to be around 40,000 years old. Researchers achieved this breakthrough by bombarding ancient materials with neutrons in a reactor core, highlighting the critical role that ochre played in prehistoric human society.
Ochre, a natural clay pigment abundant in iron compounds, is one of the most historically significant materials used by humans. It can produce a spectrum of colors, from deep yellows and bright oranges to rich reds and rusty browns.
Throughout history, ochre has served numerous purposes, including cave paintings, body decoration, personal adornments, and ceremonial uses. Beyond its visual appeal, the pigment has antibacterial properties, suggesting its potential medicinal applications in early human communities.
To explore the historical significance of ochre in Stone Age Africa, researchers utilized a variety of scientific methods to analyze samples collected from Lion Cavern and neighboring areas in Eswatini, a landlocked nation in Southern Africa.
Through optically stimulated luminescence—an innovative technique that dates materials by measuring the radiation from mineral grains exposed to sunlight—the researchers determined that ochre had been mined from Lion Cavern in substantial quantities at least 40,000 years ago.
Evidence indicates that people frequently returned to this region for ochre extraction over millennia, suggesting that the quality of the ochre was crucial to the cultural practices and knowledge that were passed down through generations.
Additionally, the team employed neutron activation analysis to assess the chemical makeup of the ochre artifacts and trace their origins.
“We collect small samples of ochre artifacts and safely activate them to become radioactive by exposing them to neutrons in the reactor core,” stated Brandi L. MacDonald, a chemistry professor at the University of Missouri.
“As these radioactive materials decay, they emit distinct energies in the form of radioisotopes, which we can measure using gamma-ray spectrometry,” MacDonald explained.
This chemical analysis revealed that ochre from this area had been transported over long distances, indicating the existence of organized trade networks and sophisticated societal structures.
The findings underscore the profound cultural and practical importance of ochre in Stone Age Eswatini, illustrating its central role in human history.
“By comparing the sources of ochre with the locations where people lived and utilized these materials between 2,000 and 40,000 years ago, we can track how their material choices evolved over time,” MacDonald noted.
“This research situates human activities in a specific historical context, demonstrating how cognition and social networks developed alongside these practices. Understanding how early humans mined, processed, transported, and used ochre offers insights into their technological advancements and sheds light on the history of human creativity and symbolism,” she added.
