Research reveals humans used ‘high-tech’ glue 100,000 years ago

By Stephen Beech via SWNS

Early humans were using high-tech 'glue' made from a local conifer in Africa 100,000 years ago, a new study has revealed.

Scientists say it may even have been a "turning point" in human cultural evolution.

In the Middle Stone Age, early Homo sapiens utilized adhesive made from local Podocarpus trees to attach stone tools to wooden spears.

Scientists say the substance has "excellent" adhesive properties and can only be produced via an "elaborate" process.

Dr. Patrick Schmidt and Ph.D. student Tabea Koch, from the University of Tübingen in Germany, mapped out the production in a joint study with Professor Edmund February from the University of Cape Town in South Africa.

The research team says the fact that early modern humans did not resort to more readily available adhesives tens of thousands of years ago is a testament to their innovative abilities and skills.

Yellowwoods, conifers of the genus Podocarpus, are tropical evergreen shrubs and trees.

Dr. Schmidt said: "Adhesives have been discovered at several Middle Stone Age sites in South Africa, mostly as residues on scrapers or stone blades that had been glued to handles or spears.

"Chemical analysis had shown that such glue was often extracted from yellowwoods. This is surprising because yellowwoods do not exude tree resins or any other sticky substance."

The team investigated how the adhesive could be made when only Stone Age materials and tools were available.

Dr. Schmidt said: "The leaves of the yellowwoods contain small amounts of resin, which you have to distill out."

The team discovered two ways to manufacture the glue.

Dr. Schmidt said: “It’s quite simple to burn the leaves directly next to flat stones.

"This leads to the condensation of tar, which can be scraped off the stones. This is a process that people may have discovered by accident."

He said the second option is more difficult and time-consuming. In it, the leaves have to be heated in a kind of underground distillery for several hours, so that the tar drips into a container. It is not known which method was used.

Dr. Schmidt says that either way, it was astonishing that early modern humans at that time did not use any plants other than yellowwoods as sources of glue.

"People could have simply collected tree resin." Koch said. "In several species that occurred in their environment, it flows visibly from the trunk. And some plants release sticky latex when the leaves break off."

The team found the explanation with the help of standard laboratory tests, such as those used in the adhesives industry:

Dr. Schmidt said: "Our tar distilled from yellowwoods had particularly good mechanical properties and proved to be stronger than all other naturally occurring adhesive substances of the Stone Age in South Africa; it was able to hold significantly larger loads."

He added: "People weren't selecting materials based on their properties, they were modifying the existing material.

"Such new engineering technology required higher cognitive abilities and innovative thinking."

The findings were published in the journal Proceedings of the National Academy of Sciences (PNAS).