In a gripping instance of Stone Age survival, Neandertals used a tarlike substance to fasten sharpened stones to handles as early as 70,000 years ago, a new study suggests.
Stone points and sharpened flakes unearthed in Syria since 2000 contain the residue of bitumen — a natural, adhesive substance — on spots where the implements would have been secured to handles of some type, according to a team led by archaeologist Eric Boëda of University of Paris X, Nanterre. The process of attaching a tool to a handle is known as hafting. The Neandertals likely found the bitumen in nearby tar sands, the team reports.
Stone tools of the type found at the Syrian site are typically attributed to Neandertals. These evolutionary cousins of modern humans frequently used bitumen and other tars as an adhesive for hafting and perhaps sometimes as a sleeve to protect a tool user’s hand, the researchers propose in the December Antiquity.
The new age of 70,000 years ago places the practice earlier than a previous finding in 1996 by Boëda’s team of 40,000-year-old stone artifacts unearthed at the same location, Umm el Tlel. Those artifacts also contained remnants of bitumen (SN: 4/13/96, p. 235).
“The surprising thing, to me, is that we do not find more such evidence for hafting by Neandertals,” remarks archaeologist John Shea of Stony Brook University in New York. Hafting may have been too time-consuming for Neandertals in some resource-poor locales, Shea hypothesizes, because their large bodies dictated that they forage constantly for food. Neandertals living at Umm el Tlel 70,000 years ago apparently had time for hafting, using bitumen to construct hunting spears, in his view.
Neandertals and modern humans inherited the intellectual abilities needed for hafting from a common ancestor that lived more than 200,000 years ago, Shea speculates.
Following an analysis of microscopic wear on 90,000-year-old stone artifacts from an early Homo sapiens site in Israel, Shea reported in 2007 that some stone points had probably been attached to hand-cast spears with an unidentified adhesive. Also in 2007, archaeologist Marlize Lombard of Natal Museum in Pietermaritzburg, South Africa, reported that modern humans living in southern Africa around 60,000 years ago hafted stone points using an adhesive made from a mix of resin and ground pigment.
In 2006, Italian researchers found two sharpened stones, dating to more than 100,000 years ago, that Neandertals had apparently attached to handles using birch-bark tar. The tar-stained stones lay among the bones of an animal that belonged to a now-extinct elephant species.
In the new study, Boëda’s team identified black stains on 200 out of more than 1,000 stone implements excavated from several related sediment layers at Umm el Tlel. Seven pieces of burned flint found in those newly excavated layers were dated to 70,000 years ago using a method that measured the radiation dose that had accumulated since the artifacts had been heated.
Black residue on stone tools clung to areas that had been grasped by hand or attached to handles, the researchers note. Geochemical analyses revealed a close correspondence between bits of residue extracted from three artifacts and bitumen collected from tar sands located 40 kilometers from the Syrian site.
A closer investigation showed that the ancient residue and modern bitumen shared nearly identical chemical compositions.
The researchers then made an adhesive out of bitumen mixed with quartz and gypsum and applied it in various amounts to 10 experimentally produced stone implements. After drying, the mixture displayed microscopic features much like those of residue on the Umm el Tlel artifacts, the scientists say.