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Neanderthal glue was much bigger than we thought

Color photo of a birch bark roll, a tar puddle and a birch tar spear to ensure the spot.

This replica shows how Neanderthals could have used birch tar to haft a projectile point.

Paul R. B. Kozowyk

Fifty thousand years ago, a Neanderthal who lived in northwestern Europe placed birch tar on the back of a sharp flint flake for easy tool handling. Eventually, this tool went down the Rhine or Meuse rivers and into the North Sea. In 21st century, dredging ships collected it along with tons of sand, other stone tools and fossilized bones, then threw the entire pile on Zandmotor Beach in the Netherlands.

Despite all this, birch tar still clung to the flake and provides evidence that Neanderthals used a complex set of technology to make elaborate tools.

Living on the edge

Making birch tar is a fairly complex process. It takes several steps, a lot of planning and detailed knowledge of materials and process. Therefore, the fact that archaeologists found a handful of birch tar tools tells us that the Neanderthals were (pardon the pun) quite sharp.

But Zandmotor's beach flake tells us more than that. Making birch tar adhesive for tools was so routine that Neanderthals used it even for a simple household tool like a small flake – even in the extreme Ice Age environment in northwestern Europe, shaded by glaciers on the northern edge of where Neanderthals could survive. And all the time, they were using very advanced methods for more efficient production.

"In spite of [the] increasing evidence, the degree of technological expression of Neanderthals is still under debate, ”notes the new article by archaeologist Marcel Niekus and his colleagues (Niekus is at the Dutch Stone Age Research Foundation). "Neanderthal tar discoveries provide evidence of a complex technology so ingrained in its behavior that it was kept within the limits of its ecological tolerance: the glacial northwestern Europe."

There is not much room to debate Neanderthal intelligence in the face of evidence that they used fire and created art. But a technology like tar adhesive production – just one component of a complex multi-part tool – requires more than brains. Anthropologists generally assume that such technologies require a larger and relatively sedentary population; hunter-gatherers can still make it, but they need to live in larger groups and move less than the archaeological record suggests to Neanderthals.

To our knowledge, Neanderthals lived in relatively small groups, with a sparse population spread across the Eurasian landscape. Based on the shape of their femurs, they walked much farther than modern hunter-gatherers. Most anthropologists do not expect them to develop, much less routinely practice, a technology that is as complicated as ceramics or metallurgy. But now it seems so.

High technology and efficient

When Niekus and his colleagues examined the thick black tar with a CT scan, they noticed fine grains of coal, sand and iron oxide mixed with the tar. These contaminants were mixed very evenly, as if they had worked on the tar while it was melting and flowing. To manage this type of complete mix, birch tar would have to reach temperatures of 350 ° C or higher. The amounts of chemical compounds like botulin and lupeol in tar also suggest a temperature in this range. To make tar so hot, Neanderthals must have produced it relatively high in technology.

As one study pointed out earlier this year, it is not too difficult to produce birch bark tar; Burning a roll of birch bark next to a flat rock will do the trick. But this is also a super inefficient way to produce tar; Niekus and his colleagues – who experimented with tar production for the sake of science – estimate that it would take ten hours to produce enough tar just to trigger a single flake. If Neanderthals had the trouble of placing the tar in a small, everyday household tool like a flake (whether you want to attach it to a handle or just for a simple squeeze), producing tar in usable quantities must have been routine. And that means they probably found a more efficient way to do it.

The most efficient way to get birch bark tar is to heat the bark roll in a clay pot buried inside a mound of soil. It is a more complicated process, requiring more steps, more planning and more detailed technical knowledge, but it also produces more tar faster and with about 40 times less bark required for the same amount of tar. It is also the only method that produced temperatures hot enough to explain fine grains of sand and coal mixed with tar (360 ° C inside the ship and 310 ° C inside the shell roll).

The mother of invention

Therefore, the Zandmotor Beach flake suggests that Neanderthals used Stone Age technology to make stickers for their multipart tools (which were quite high-tech in themselves). It involved a complex process of collecting birch bark and heating it to extract the tar and then using it to pull a tool or shape a handle. That would take a lot of time and energy, but "the technology investment must be worth it," wrote Niekus and his colleagues.

This is especially true in an extreme environment such as northwestern glacial Europe 50,000 years ago, where resources were scarce and uncertain, and just surviving on a basic level must have been a challenge. But Niekus and his colleagues suggest that the cold and inhospitable environment may indeed have led Neanderthals to develop more complex tools and more efficient ways to produce them in order to make a living.

PNAS, 2019. DOI: 10,1073 / pp.1907828116. (About TWO).

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