Neanderthals died out just as our species—Homo sapiens—spreading from Africa, arrived around 40,000 years ago. If the claim is correct, it helps cast doubt on previous assumptions that Neanderthals lacked the abilities of modern humans to plan ahead, innovate, and communicate through language, art, and symbolism. There is a growing weight of evidence that we may have underestimated Neanderthal skills and behavior, and that they were not the lumbering, dim-witted cartoon cavemen of popular legend. At the same time, many questions remain contentious—for instance, whether Neanderthals had language, intentionally buried their dead, or regularly used mineral pigments to decorate their bodies.
Ingenious and Industrious
The claim investigated by NOVA is that Neanderthals invented a glue essential to producing their most formidable hunting weapon, a flaked stone spear tip fitted to a wooden shaft. They attached the stone to the shaft by winding animal sinew or some other type of binding around the joint and then smearing glue over it. Discoveries at Neanderthal sites in Syria and Romania show that, to obtain glue, they sometimes used natural deposits of bitumen or asphalt, in one case, fetched from over a dozen miles away. At the Syrian site, the bitumen had been heated up to make the thick liquid easier to apply.
At other sites, the Neanderthals subjected sticky substances to a much more elaborate process. Birch bark contains a tacky resin known as pitch that is impossible to extract simply by tapping into the tree, as with pinesap or maple syrup. Instead, the pitch must be separated from the bark by a process known as dry distillation. Chemists have discovered that distilling pitch from birch bark requires an oxygen-free environment and sustained temperatures of over 650° F. How could Neanderthals, with their Stone Age technology, have produced such conditions? If they really did master this complex process, it is hard to resist the conclusion that they must have had language and a sophisticated ability to think and plan ahead.
Two small, hardened lumps of black material were found during the dig, one bearing a fingerprint and the other the impression of a wooden haft or handle.
Evidence indicates that they successfully developed such a technique. The first discovery was made in 1963 at Kínigsaue, in then-East Germany. This was the site of an ancient lakeside hunting camp, from which Neanderthals had hunted now extinct Ice Age creatures such as mammoth and woolly rhino as well as red deer, horses, and reindeer. Two small, hardened lumps of black material were found during the dig, one bearing a fingerprint and the other the impression of a wooden haft or handle.
In 2001, the lumps were dated to at least 40,000 years ago and were shown to have the chemical signature of birch bark pitch produced by the dry distillation process. Much older evidence was found at the Campitello quarry in central Italy. Here, the remains of an extinct elephant lay close to two large lumps of black pitch, which covered the end of two stone flakes crafted in a typical Neanderthal style. The Campitello find dates back over 200,000 years, a remarkably early origin for this complex process. A third Neanderthal site at Inden-Altdorf, overlooking the Inde River in Germany and dating to around 128,000 to 115,000 years ago, features more than 80 stone tools flecked with black material, but the chemical analysis indicating that this was distilled pitch requires further confirmation.
Before Their Time
Pitch production only began on a large scale in Europe during the Middle Ages, around 1,000 years ago. Pieces of birch bark were typically rolled up inside a double-walled clay pot, which was sealed to exclude the air and placed in a kiln or fireplace. But the process was known in Europe long before that. The famous 5,300 year-old "Iceman," nicknamed ítzi—a naturally mummified body found in 1991 on a high mountain pass in the Tyrolean Alps—carried some 20 items of equipment, including a copper axe and flint-tipped arrows. Birch bark pitch was used to glue the axe to a handle carved from yew, while the arrowheads were bound and glued to shafts made from shoots of the Viburnum tree. In addition, ítzi carried some of his gear in two bark containers, so during ítzi's time, birch bark was evidently a versatile and important material.
Special clay vessels like those used in the Middle Ages have not been found in ítzi's era, nor did pottery exist in Neanderthal times. But the archaeologists at Inden-Altdorf found an important clue: upon analyzing the pitch smeared on Neanderthal tools at the site, they detected traces of potassium, sulfur, and calcium, evidence that the material had been directly exposed to fire and ash during its manufacture. After some practical experiments, the team proposed that the Neanderthals had invented the following procedure: first, wrap a long strip of birch bark around a small pebble so that it forms a cigar-shaped roll. Next, dig a narrow pit, then set light to one end of the roll and place the burning end at the bottom of the pit. In the confined space at the bottom of the pit, the smoldering bark quickly uses up oxygen and causes the pitch to "sweat," or condense, out of the roll of bark onto the surface of the pebble. While still hot, the pitch is a sticky liquid that can be used immediately as glue.
"Neanderthals were very capable pyrotechnologists."
Simple though it sounds in theory, the technique is highly challenging in practice. Although German experimental archaeologist Friedrich Palmer succeeded in earlier published experiments, in the NOVA program, he fails to produce more than a thin smear of pitch. In 2010, another team reported success by a variation on the technique: lay strips of bark on a flat stone surface, cover them with a couple of inches of sand to exclude oxygen, then build a fire on top. After a little over an hour, the team dug up the stone and found that enough pitch had dripped onto its surface to haft two or three spears or tools. However, the team succeeded easily on their first attempt only because they had a thermometer to judge if the fire was hot enough. Without such an aid, managing the fire proved very difficult, particularly in windy weather. Even with a windbreak, it required multiple attempts over many days to achieve success.
Whatever technique is used, procuring pitch today with Stone Age methods obviously calls for careful attention and considerable skill and judgment. Too low a temperature, and the bark fails to produce any pitch; too high, and the bark becomes hard and brittle; with too much oxygen, the bark burns up. As the experimental tests have shown, the temperature of the fire must be constantly monitored in varying wind conditions, the birch bark must be buried correctly with oxygen excluded and removed from the fire at the right time. Archaeologist Wil Roebroeks, who witnessed Palmer's NOVA experiment, comments that its failure underscores the complexity of the process, which "goes to show that they [the Neanderthals] were very capable pyrotechnologists. We're still learning how they did it a quarter of a million years ago."
Roebroeks adds that the significance of the Neanderthal pitches should not be overblown. "After all, they were produced by hunter-gatherers who survived in western Eurasia for hundreds of thousands of years in a wide variety of environments, successfully exploiting a wide range of mammals and other resources...That they discovered a trick or two which we are unable to reproduce nowadays should not come as a surprise—unless of course one assumes that they were 'complete idiots,' lacking the flexibility and learning capacities of other primates."
While Roebroeks warns about making too much of the glue finds, for other archaeologists, the mere fact that Neanderthals could make multi-part tools and weapons argues that they were capable of planning in depth, coordinating several tasks at once, and conceptualizing past and future. No single category of evidence can decide the case for the status of the Neanderthal mind, but the intriguing story of birch bark pitch joins a growing list of discoveries that indicate we may have underestimated the closeness of our bond with our long-vanished relatives from the Ice Age.