Archival view of lake sediment at Mundafan, not the excavation reported in 2026. Crassard et al., PLOS ONE (2013), Fig. 5C, CC BY 4.0; cropped.
There were hippos in Saudi Arabia’s Empty Quarter. That sounds like a terrible place to put a hippo until you find out what used to be there: a freshwater lake big enough to reshape the map.
On that vanished shoreline, researchers found flint tools, animal fossils and traces of plants that people handled roughly 125,000 years ago. A few stone points carried something more surprising. In a study published November 12 in Science, the team reported impact damage and chemical traces it identified as plant poison.
The lake left more than a watermark
The site, ‘Uruq Aljelibah, sits beside the former Lake Mundafan in southern Saudi Arabia. Today the basin is dry, but pale layers of sediment still show where water once collected. The study team estimated the ancient lake could have covered about 340 square kilometers, or 130 square miles, and reached roughly 29 meters deep. Those are reconstructed dimensions, not a measurement of where the shore sat on any particular day.
The fossils tell the story from ground level. Alongside the hippos were buffalo, gazelles, camels and ostriches. The researchers dated sands and fossil teeth and used the sediments and aquatic remains to piece together a wetter landscape with freshwater and open grasslands. It was a place where people could find animals, plants and material for tools without leaving the lakeshore behind.
What the flint still carries
The team collected more than 5,500 stone tools larger than two centimeters in its main study area. Some broken pieces fit back together, which helps show that people were making tools on the shore, not just dropping finished ones there. For a view of the actual site, KAUST’s announcement shows the excavation; the cover photograph shows a different location in the same basin.
The chemical traces are a clue, not a complete weapon. The researchers found impact damage on several points alongside residues they associated with a toxic plant. Other traces of resin and wood are consistent with mounting stone tips onto handles or shafts. Together, the study argues, these clues point to hunting equipment that may have used poison. They don’t tell us whether a particular point came from a hand-thrown spear or another weapon, or what animal it struck.
Elsewhere on the stone tools, residues suggest people worked with tubers, palms and other plants. The lake is gone, and so are the wood and fibers that once mattered as much as the flint. But even after 125,000 years, the surfaces of those stones still carry traces of the work people did there.
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