The intricate process behind Neanderthal adhesives.
Neanderthals developed a method of generating a glue derived from birch tar to hold their tools together about 200,000 years ago, which was waterproof and didn't decompose. Researchers found evidence that this glue wasn't just the original tar; it had been transformed in some way. The team tried several different processing methods and found that Neanderthals distilled tar in an intentionally created underground environment that restricted oxygen flow and remained invisible during the process. This degree of complexity is unlikely to have been invented spontaneously.