Stone blades found in Sibudu Cave, near South Africa’s Indian Ocean coast, bear traces of compound adhesives that once joined them to wooden hafts to make spears or arrows.
Why is this so cool? Because by systematically replicating the ancient glues, using only Stone Age techniques and ingredients, the researchers discovered that ocher improves the bonding capacity of such natural adhesives as acacia gum. They also learned that those ingredients are highly variable in chemical composition and thus in key characteristics, such as viscosity, that affect the strength of the bond.
To make an effective glue, say the researchers, ancient artisans would have had to adjust their recipes in real time to compensate for unpredictable ingredients, staying mindful of their goal while shifting their focus back and forth among the various steps in the process.
So maybe they were just mad scientists! Mwahahaha!