This is how Neanderthals made glue from tree bark

Glue and other adhesives make life easier for everyone, and so it's no surprise that rudimentary forms of it can be traced back to ancient times. Whereas modern glue comes in many varieties for many purposes, ancient glues were made from natural substances, and the exact process that went into making the compounds isn't clear. A new study, however, may shed light on the answer.

At this point in time, the oldest known glue in existence was made by Neanderthals around 200,000 years ago who used it, in part, to craft weapons. One example is shown above: a spear with a sharpened piece of flint held in place on the wood shaft via a tarry substance. That substance comes from birch bark, and a new study details three different ways Neanderthals may have formed the glue.

The simplest method in terms of complexity — but the least likely to produce any significant quantities of tar — was simply lighting the bark on fire and scraping up whatever tar remained. To avoid burning up the tar, though, the fire would have to be kept within what researchers describe as a fairly narrow temperature range, which would have been difficult given the rudimentary tools that Neanderthals had access to.

To get the lower temperature, Neanderthals would had to have put hot embers and ashes onto the bark, resulting in tar. In one case, that could be achieved by rolling up the birch, while in another experiment it was found possible to get tar by leaving the bark rolled and suspended over a fire with embers on top.

The third possible way Neanderthals made tar was by forming a container of sorts out of the bark, then placing the container in a pit covered with dirt and more bark. A fire was lit over the pit and, if sustained long enough, would render the bark into larger quantities of tar. It is possible that all three methods or some variation of them were used at different times based on how much fuel was available, how much time was available to dedicate to making tar, and how much tar was needed.

SOURCE: ScienceDaily, Nature