Neanderthals were making glue from birch bark 200,000 years ago
Three stone tools found in central Italy, about 200,000 years old, still carry traces of birch bark tar used to fix them to wooden handles. They are the oldest known hafted tools of their kind, and they show that people were cooking up adhesives long before our own species reached Europe.
Glue, paste, cement or mucilage: whatever the label, an adhesive is a non-metal spread on surfaces to bond them and keep them from separating. Compared with stitching, bolts or welding, it can join unlike materials, spread stress more evenly across a joint, suit automated production and free up design. Its weak points are heat, large objects joined over small areas, and the difficulty of taking parts apart for testing.
Making tar from birch bark was long assumed to need sophisticated dry distillation, but a 2019 experiment showed an easier route: burn the bark beneath an overhanging rock in the open and scrape off the tar that collects on the stone. Single-ingredient plant glues can be brittle and fail in damp conditions, so people began mixing. At Sibudu in South Africa, 70,000-year-old stone pieces once set into hafts were coated with plant gum blended with red ochre, which toughens the gum and protects it from moisture. At Le Moustier, Middle Paleolithic toolmakers, possibly Neanderthals, combined ochre with bitumen to make grips.
Later uses turn up everywhere. About 6,000 years ago, people buried their dead with food in clay pots mended with tree resin, and Babylonian temple statues from around 4000 BC had ivory eyeballs fixed with bitumen. Otzi, the 5,200-year-old man found in a glacier on the Austria-Italy border, carried arrows and a copper hatchet bonded with pitch made by heating birch tar.
Written mentions of glue begin around 2000 BC. Egyptian tomb paintings show wood being glued, and Tutankhamun's burial held a casket assembled with glue; Egyptians laminated wood for bows and furniture with casein, a milk protein, and pasted papyrus with starch. Greeks and Romans advanced the craft further, yet glue did not become common in Europe until roughly 1500 to 1700, and synthetic adhesives took off only in the 20th century.
Source: Adhesive
