In 1983, archaeologists working at Kruger Cave in South Africa unearthed a remarkable find: a 7,000-year-old antelope femur bearing unusual markings. X-ray analysis later revealed three arrowheads embedded within the bone, suggesting an advanced method of hunting for its time.
For nearly four decades, the artifact remained stored at the University of Witwatersrand’s archaeology department. Renewed interest emerged in 2022 when researchers revisited the cave in the Magaliesberg Mountains to conduct further examinations.
Professor Matthew Sponheimer from the University of Johannesburg led the latest analysis. He and his team suspected the femur held more than just sediment and degraded marrow. Their prior research on a 500-year-old medicinal container in the Eastern Cape had provided valuable insights, inspiring them to apply similar techniques to this ancient artifact. Their tests uncovered a complex mixture of toxins, including two plant-derived compounds and traces of a third unidentified substance.
Using advanced micro-CT scanning, the team reconstructed the femur in 3D, revealing new details unseen in the original 1980s X-rays. The scans exposed an unusual material within the bone cavity, hinting at a connection between the embedded arrowheads and the chemical traces present.
Further chemical analysis confirmed the presence of two potent cardiac glycosides: digitoxin and strophanthidin, both known to disrupt heart function and historically used as arrow poisons. Additionally, the researchers detected ricinoleic acid, a marker of ricin degradation, one of nature’s most toxic substances.
The presence of multiple toxic compounds suggested an advanced understanding of venom preparation among prehistoric hunters. Rather than relying on a single poisonous plant, they blended extracts from different species to enhance potency, demonstrating a sophisticated approach to weaponizing natural substances.
Throughout history, hunters across the globe developed methods to extract and apply poisons for more effective kills. In southern Africa, early human groups excelled in refining these techniques. The oldest known evidence of poison use in the region comes from Border Cave, where a 24,000-year-old wooden spatula bearing traces of ricinoleic acid was discovered. This simple toxin would later give way to more intricate chemical mixtures.
Elsewhere, sites such as Kuumbi Cave in Zanzibar yielded 13,000-year-old arrowheads that may have contained traces of venom, though no definitive chemical analysis has confirmed this theory.
More recent examinations at Kruger Cave also studied a 1,000-year-old arrow. Unlike the femur, its chemical traces had significantly deteriorated over time. This contrast highlighted the protective properties of bone, which helped preserve the toxins far longer than other materials exposed to the elements.
The findings from Kruger Cave provide compelling evidence of prehistoric hunters’ deep knowledge of plant-based toxins. Their ability to craft effective poison mixtures points to a level of ingenuity and resourcefulness that shaped early hunting strategies and survival techniques.
