A flint tool coated in birch tar and dredged from the bottom of the North Sea has shed new light on Neanderthal tool use, and demonstrated mobile small populations can develop more advanced technologies than some anthropologists have believed. Although the discovery resembles other, older, Neanderthal tools, it shows that one of their most advanced innovations was in use at the very edge of their habitable range.

Fifty thousand years ago the North Sea was a wide plain, but with glaciers covering most of Britain the region was so cold, it would have stretched the capacity of Neanderthals to inhabit it. Most of the fossils left behind from that era have remained beneath the waves where we cannot access them. However, as part of an attempt to buttress Zandmotor beach in the Netherlands, the seafloor nearby is dredged for sand to counteract erosion. In 2011, a flint tool was found among the newly dumped sand.

The flint itself is not all that unusual, but Marcel Niekus of the Foundation for Stone Age Research reports in Proceedings of the National Academy of Sciences the tar covering around half of it is very revealing indeed. Carbon dating reveals the tar to be at least 47,000 years old. It is thought tar was primarily used as an adhesive in the era, attaching flint tools to wooden hafts of spears or axes to make them far more powerful. However, it may sometimes also have been used simply to make tools easier for the user to grip.

Making tar, on the whole, was not easy. We don’t know how exactly Neanderthals, or early modern humans for that matter, made their tar from birch, but three methods considered possibilities require the collection of enormous amounts of bark to produce very small quantities of tar. A fourth method is much more efficient, but also more complex and sophisticated. Even the simplest method of tar production requires a “3-level hierarchically organized facility, with different components made to function together,” the paper notes, and contaminants in the Zandmotor discovery strongly indicate it was made using the most complex method.

The harshness of conditions in the area meant the tar's makers must have moved frequently to avoid over-using the local resources. For the same reason, the area would have been sparsely populated. Since Neanderthals could not walk long distances as easily as modern humans, opportunities to share ideas and develop the sort of technologies that require many advances, rather than being the product of a single genius would have been limited.

Both high population density and long-term occupation of sites have been proposed as necessary features for complex technologies, but this finding refutes both, as well as adding to the evidence Neanderthals were our equals in creativity and intelligence.