Oldest known poison arrows were used to hunt animals 60,000 years ago

Scientists have detected traces of plant toxins on Stone Age arrowheads that were used by hunter-gatherers in South Africa about 60,000 years ago. Marlize Lombard/University of Johannesburg via CNN Newsource

Scientists have detected traces of plant toxins on Stone Age arrowheads that were used by hunter-gatherers in South Africa about 60,000 years ago.

The find marks the oldest known poison arrows and indicates that such tools and sophisticated hunting strategies existed thousands of years early than previously thought, according to the authors of a study published Wednesday in the journal Science Advances.

“In persistence hunting, poisoned arrows did not usually kill prey instantly,” said lead study author Sven Isaksson, professor of archaeological science at Stockholm University’s Archaeological Research Laboratory. “Instead, the poison helped hunters reduce the time and energy needed to track and exhaust a wounded animal.”

Two different alkaloids, or organic plant compounds, found in the poisonous chemical residue were from the gifbol plant, or Boophone disticha. Traditional hunters in the region still utilize the plant today and refer to it locally as poison bulb.

Hunter-gatherers likely dipped the quartz arrowheads, excavated from the Umhlatuzana Rock Shelter in KwaZulu-Natal, South Africa, in 1985, in poison before using them to kill animals for food. The presence of poison arrows during the Late Pleistocene suggests that hunter-gatherers knew which plants to use, as well as how long it would take for the toxins to be effective.

“Understanding that a substance applied to an arrow will weaken an animal hours later requires cause-and-effect thinking and the ability to anticipate delayed results,” Isaksson wrote in an email. “The evidence points to prehistoric humans having advanced cognitive abilities, complex cultural knowledge, and well-developed hunting practices.”

Identifying a poisonous plant

While humans have long relied on plants as food, poison arrows are just one example of how our ancestors living during the the most recent ice age exploited the chemical properties of plants to develop medicine and toxic substances, Isaksson said.

Hunters could have applied poison to the points, also called backed microliths, by stabbing the gifbol plant’s bulb, or by cutting the bulb and capturing the poisonous substance in a container. The poison may have been concentrated by applying heat or exposing it to sunlight, according to the study.

Poisons work in different ways, with some varieties like myotoxins destroying muscle tissue and others, called neurotoxins, attacking the nervous system. Hunter-gatherers may have avoided any part of the animal affected by myotoxins, whereas neurotoxins would be diluted after spreading throughout the animal’s body, Isaksson said.

“Some toxins are only dangerous if they enter the blood stream and are not harmful when ingested,” he said via email. “Others may be easily destroyed by heat and thus neutralized by cooking.”

Chemical analyses showed the presence of the alkaloids buphandrine and epibuphanisine on five of the 10 quartz arrowheads. Despite being buried for thousands of years, the arrowheads still retained residue because the alkaloids have specific chemical characteristics that enabled them to endure, like the fact that they don’t dissolve easily in water.

Even small quantities of the plant’s toxins can be lethal to rodents within 20 to 30 minutes and can cause nausea, respiratory paralysis, edema of the lung, feeble pulse and other symptoms in humans, according to the study.

For comparison, the authors also examined four 250-year-old arrowheads collected in South Africa and brought to Sweden. The analysis found that their points were laced with the same toxic alkaloids, suggesting the long history of traditional use of the poison in hunting, the authors said.

“Finding traces of the same poison on both prehistoric and historical arrowheads was crucial,” Isaksson said. “By carefully studying the chemical structure of the substances and thus drawing conclusions about their properties, we were able to determine that these particular substances are stable enough to survive this long in the ground.”

A peek inside a prehistoric lifestyle

Archaeologists have intuited that people living in the later Pleistocene must have had some knowledge of plant toxins and used them to aid in hunting, but direct evidence has been hard to come by, said Justin Bradfield, associate professor at the University of Johannesburg’s Paleo-Research Institute. Bradfield was not involved in the new study.

Organic molecules often break down over time, making it difficult to reconstruct original compounds, but Isaksson and his team did an admirable job of chemically verifying tiny, serendipitously preserved residues to show hunter-gatherers’ understanding of toxic plants, he added.

“It also shows advanced planning, strategy and causal reasoning — something that is very difficult to demonstrate for people living so long ago, but for which the evidence is nevertheless increasing every year,” Bradfield said.

Prior to the discovery of poison residue on the Umhlatuzana arrow tips, the earliest direct evidence of poison on hunting tools came from bone-tipped arrows in an Egyptian tomb 4,431 to 4,000 years Before Present as well as Kruger Cave in South Africa about 6,700 years Before Present, according to the study. Archaeologists and geologists use Before Present as a timescale in which 1950 is fixed as the present year because it’s when radiocarbon dating was introduced.

Other evidence of the use of poisonous hunting tools has been unearthed in Border Cave in South Africa’s KwaZulu-Natal province: an applicator that may have been used to put poison on arrow tips dated to 24,000 years ago, and a lump of beeswax dating back 35,000 years that might have served as an adhesive to attach an arrow point.

The study also confirms that the bow and arrow was a signature piece of technology as humans spread across the globe, and reveals a cognitive distinction between prehistoric hunter-gatherers representing Homo sapiens and other hominins like Neanderthals, said Ludovic Slimak, an archaeologist at the French National Centre for Scientific Research and Paul Sabatier University in Toulouse, France. Slimak did not participate in the research.

“This strengthens the view that the bow is not a late invention, but a fundamental and complex technology whose origins go back at least 80,000 years in Africa and Asia, and which later accompanied the arrival of Homo sapiens in Europe around 54,000 years ago,” Slimak added.

Isaksson and his collaborators are eager to investigate other promising sites in South Africa to see how widespread poison arrow use might have been at the time.

“It tells us something new about how people at that time thought, planned, and understood the world around them,” he said.

By Ashley Strickland, CNN