Pleistocene-era humans utilized poisoned weaponry, as stated by recent chemical analyses revealing toxic plant-derived alkaloids on 60,000-year-old stone age arrowheads. ‘This finding indicates that archery was employed by people earlier than previously thought, and that they effectively poisoned the tips,’ states Femke Reidsma, a bioarchaeologist from the University of Leiden who did not participate in the study.
The most ancient direct evidence of human use of poisoned arrows originates from the Holocene, starting 11,700 years ago. Bone arrow points treated with cardiac glycosides were unearthed from Kruger Cave in South Africa and approximated to be 6700 years old. Nevertheless, indirect evidence led researchers to hypothesize that the practice of hunting with poisoned arrows commenced much earlier.
The arrowheads examined in this study were retrieved from Umhlatuzana Rock Shelter in South Africa in 1985 during road work. They were housed in the KwaZulu-Natal Museum, remaining untouched until 2005, when researchers selected 10 quartz arrow tips with visible residue for chemical examination.
Employing GC-MS, the team identified plant-based toxic alkaloids on half of the artefacts analyzed. Most significantly, they detected buphanidrine and epibuphanisine, toxins that derive from the roots of Boophone disticha, a plant renowned for its application as arrow poison.
‘Initially, I was apprehensive about the time depth and age of the samples, and did not foresee any detectable traces,’ remarks Sven Isaksson from Stockholm University, Sweden, who contributed to the research team. ‘When the mass spectra of buphanidrine and epibuphanisine were verified, cross-verified, and confirmed multiple times in five of the samples, it wasn’t a Eureka moment, but certainly a “Yes!” moment.’
As a control, the researchers also investigated residues from known poisoned arrows gathered in the 1770s, in addition to a modern extract of B. disticha. Every sample tested positive for buphanidrine.
‘[B. disticha] is one of the best-known botanical components employed by the Bushmen between the 18th and 20th centuries for hunting poisons,’ clarifies Justin Bradfield, who examines poison residues on stone age weaponry at the University of Johannesburg. ‘It also possesses numerous other uses.’ Commonly termed gifbol (poison bulb), its leaves and outer scales were utilized medicinally or as preservatives.
The authors theorize that the buphanidrine molecules have withstood degradation for an extended period due to the stable and arid conditions of their deposition site, alongside their chemical properties.
‘[Buphanidrine] comprises five hydrogen bond acceptors, no hydrogen bond donors, and merely two rotatable bonds. The presence of hydrogen bond acceptors indicates that buphanidrine can interact with mineral surfaces, such as silica, becoming adsorbed and thus protected,’ elucidates Isaksson. ‘The lack of hydrogen bond donors results in relatively low water solubility and also renders buphanidrine less amenable to oxidation and hydrolysis, enhancing its chemical stability across various conditions.’ The alkaloids additionally exhibit antibacterial characteristics.
These discoveries contest the dominant perceptions of the intellect and technological sophistication of Pleistocene-era humans, asserts Reidsma. ‘[The findings] reveal that humans had a robust comprehension of the chemistry of these toxic plants and their utility in more efficient hunting. Handling the poison without endangering oneself can be quite challenging. They would also have been skilled in tracking prey since large animals do not succumb instantaneously to the poison.’
Bradfield concurs. ‘It also signifies advanced foresight, strategy, and causal reasoning – aspects that are extremely challenging to demonstrate for individuals from such distant eras, yet the evidence is accumulating year after year.’