Paul Kozowyk

Paul Kozowyk

Paul Kozowyk

Paul Kozowyk

Despite many recent discoveries that show Neanderthals were technologically and socially sophisticated, there's still a popular idea that these heavy-browed, pale-skinned early humans were mentally inferior to modern Homo sapiens. Now we have even more corroboration that they were pretty sharp. A fascinating new study reveals that Neanderthals were distilling tar for tool-making 200 thousand years ago—long before evidence of tar-making among Homo sapiens. And an experimental anthropologist has some good hypotheses for how they did it, too.

One of humanity's earliest technological breakthroughs was learning to distill tar from tree bark. It was key to making compound tools with two or more parts; adhesives could keep a stone blade nicely fitted into a wooden handle for use as a hoe, an axe, or even a spear. Scientists have discovered ancient beads of tar in Italy, Germany, and several other European sites dating back as much as 200 thousand years, which is about 150 thousand years before modern Homo sapiens arrived in Western Europe. That means the people who distilled that tar had to be Neanderthals.

The question that Leiden University archaeologist Paul Kozowyk and his colleagues wanted to answer was how sophisticated the Neanderthals had to be to do it. Modern-day tar is distilled between 340 °C and 370 °C, and the process requires a ceramic vessel. Maintaining a temperature in that narrow band is very difficult without specialized tools. Plus, there are no signs that anybody on Earth had developed ceramic technology until roughly 20 thousand years ago, and ceramic pots didn't come into widespread use until about 9,000 years ago.

Still, the evidence is indisputable: humans manufactured beads of tar much earlier. Kozowyk and his fellow researchers decided to figure out how by engaging in a little experimental archaeology, so they set about trying to make tar using only the tools Neanderthals had available. These included fire, ash, birch bark, sharp stones, and mesh woven from sticks. Kozowyk and his team tested three ways to make tar from birch bark, and they measured tar output, temperature, and complexity of the task.

In the "ash mound" method, a roll of birch bark is heated under a pile of ash and embers. Tar is extruded into a birch bowl. In the "pit roll" method, a tube of birch bark is inserted into a narrow pit, and fire is lit on top. Tar drips from the roll onto a rock at the bottom of the pit. And finally, in the "raised structure" method, a birch bowl is placed in a shallow pit, under a screen woven from green willow wood. A roll of birch sits atop the screen and is then buried under dirt. Fire is lit on top of the dirt, slow-cooking the birch bark.

Each method resulted in a few grams of tar, similar to amounts discovered at Neanderthal sites in Europe. But some methods, like the raised structure, were more resource-intensive, requiring a lot more firewood. Other methods, like the pit roll, were simple and easy, but yielded little tar. The researchers also discovered that they could distill tar even if the temperatures sometimes went below 200 °C and above 400 °C. It turns out that neither ceramics nor a carefully-maintained temperature are necessary to make tar.

Writing in Nature Scientific Reports, the scientists concluded that any of these methods would probably have worked for Neanderthals. They also noted that they all had the virtue of being easy to do using cooking pits. In fact, Neanderthals might have figured out how to make tar by accident when a stray piece of birch bark began to ooze tar near the fire. Then it would have been a relatively simple matter for the ancient people to figure out that tar was sticky and ultimately to deduce that it could be used to secure their tools better.

There probably wouldn't have been a "eureka" moment when Neanderthals suddenly figured out how to distill tar. Instead, they would have gone through a series of small steps and probably accidental discoveries. People all over the world probably figured out how to distill tar at different times and in different ways. Still, making tar requires complex thought, as well as the ability to combine tools and plan for the future. For this reason, Kozowyk and his team write, "Tar production in Paleolithic Europe has, in turn, been used to argue for similarities between the technological capabilities of Neanderthals and their near-modern contemporaries in Africa."

No one is certain why Homo sapiens in Africa didn't distill tar, but probably it was simply lack of access to birch trees. Ample evidence suggests that early humans in Africa and Australia manufactured ochre for use as an adhesive. So next time you use a drop of glue, take a moment to appreciate that you have just deployed one of humanity's oldest technical innovations. And it was invented by a Neanderthal.

Nature Scientific Reports, 2017. DOI: 10.1038/s41598-017-08106-7 (About DOIs).

Listing image by Paul Kozowyk