Archaeologists have found what may be among the world's oldest poisoned weapons at a site on an ancient lakeshore in southern Saudi Arabia, Live Science reported. The study, published Thursday in the journal Science, describes stone tools from a 125,000-year-old landscape known as 'Uruq Aljelibah, which means "sand dunes of a watering hole." Several stone points carried chemical residues linked to the arrow poison tree, Acokanthera schimperi, a plant historically used for toxins in eastern and central Africa and southern Arabia. "At 125,000 years old, these would be substantially older than the poisoned arrowheads recently identified in South Africa, which date to around 60,000 years ago," co-author Chris Clarkson, an archaeologist at the Max Planck Institute of Geoanthropology and Griffith University, told Live Science. "But we haven't demonstrated exactly how the poison was prepared or whether it was effective. So I'd describe these as potentially the oldest evidence for poisoned hunting weapons, rather than an unequivocally established first."
Today the site sits in the Empty Quarter, one of the hottest, driest deserts on Earth. The researchers say it was once a freshwater lake about 130 square miles (340 square kilometers) across and up to 95 feet (29 meters) deep. Fossils suggest hippopotamuses, buffalo, ostriches, camels, gazelles, oryx, palms, reeds, trees, and shrubs. "The idea of hippopotamuses and enormous buffalo living around a lake in what is now the Empty Quarter really brings home just how dramatically these landscapes, and global climates, have changed," Clarkson said. The team found more than 5,500 stone artifacts, along with preserved traces of plant materials such as fibers, resins, and wood. Several points showed impact damage consistent with hunting large animals, and a microscopic analysis found traces of animal tissue near the tips. The distribution of tools closely matched clusters of animal bones, suggesting the lakeshore was a focus for hunting and processing game.
"At most Paleolithic sites, we're lucky if we get the stone tools and perhaps a few animal bones," Clarkson said. "Here we can actually begin to reconstruct what those tools were doing." African hunters have coated spear tips and arrowheads with extracts from the same tree to paralyze or kill game. It remains unclear how people who used poison avoided poisoning themselves when they ate the meat. "A poison introduced directly into a wound doesn't necessarily behave in the same way when swallowed," Clarkson said, noting that hunters have sometimes removed the meat around a wound before eating the rest of the animal. Eleanor Scerri, a Max Planck archaeologist who was not part of the study, called the evidence "remarkable," including "the very convincing spatial relationship between hunting-related tools and the bones of animals such as hippos." Jeffrey Rose, a Paleolithic archaeologist at the University of Algarve who also was not on the team, said sites in Arabia with both stone tools and animal bones are rare, and that some of the flakes fit back together, "so the tools were made on the spot."
Rose also offered an important caution: all of the stone artifacts in this study were collected from the surface. "Not one was excavated from the layers that were dated," he said. "The 125,000-year date belongs to the lake, not to the tools. For the tools, it is only a maximum age." Clarkson said the team suspects the site most likely belonged to Homo sapiens, because modern humans had already expanded out of Africa into Southwest Asia in this period, though no human remains were found. Future work, Rose said, should look for artifacts sealed in lake beds. The verified claim is potential evidence of poison on stone points from a once-wet Arabian lakeshore, not a closed case that hunters were already tipping weapons with toxin 125,000 years ago.