Neanderthals may have treated wounds with antibiotic sticky tar

Neanderthals may have used tar made from tree bark as an antiseptic to treat wounds. Modern experiments with birch tar show that it has antibiotic properties, regardless of how it is made, and suggest that Neanderthals could have discovered its medicinal use.

The discovery adds to a growing body of evidence suggesting that Neanderthals used medicinal plants to treat injuries and illnesses.

“Birch tar as a substance has been known for a long time since the end of the Pleistocene, especially from Neanderthal sites across Europe,” says Tjaark Siemssen at the University of Oxford.

“It is quite clear that it has been used as an adhesive,” says Siemssen, for example to attach ground stone heads to wooden skewers. However, he says that may not have been the only use. In some indigenous communities in recent centuries, birch tar has been used as a medicinal salve. Among the Mi’kmaq communities of eastern Canada it is called maskwio’mi and is used as a broad-spectrum antibiotic.

To find out whether the birch tar produced by Neanderthals might have had similar properties, Siemssen and colleagues collected bark from downy birch (Betula pubescens) and silver birch (Betula pendula) on public land in Germany. They tried three methods of producing birch tar.

In the “raised structure” method, they dug a small hole and placed a container at the bottom. Above this they piled up birch bark and covered it in clay. They lit a fire on top of this pile, and after 2 hours they collected the birch tar that had dripped into the container.

The second method was much simpler and may have been the first to be tried by Neanderthals. The team burned small amounts of birch bark under a fireproof stone, causing birch tar to condense on the stone. This “condensation” method produced much smaller amounts.

Finally, for comparison, the researchers tried the modern method used by the Mi’kmaq communities. They heated the birch bark in a sealed metal box, with holes through the bottom to allow the tar to drip out.

All the birch tars were tested for antimicrobial activity. All but one were effective against Staphylococcus aureusa bacterium often found in skin infections. The strongest was the one produced from silver birch using the raised structure method. The only one that didn’t block S. aureus it was made from downy birch using the condensation method.

The experiment indicates that birch tar consistently has antimicrobial properties, even when made using low-tech methods that would have been available to Neanderthals, says Siemssen. While Neanderthals used it as an adhesive, it’s potentially quite misleading to “reduce the use case to just one single thing, when it has so many different purposes”, he says.

“I appreciate that the authors have identified some medicinal value in the birch bark,” says Karen Hardy of the University of Glasgow in the UK. However, Hardy points out that many plants have medicinal properties without the need for processing. “Obtaining birch bark is a complex, time-consuming procedure,” she says. “I think that to demonstrate their argument that it was deliberately produced for its medicinal properties, they would need to demonstrate its superior or unique value.”

Previous research has identified other evidence of Neanderthal use of medicinal plants. A Neanderthal with a dental abscess appears to have eaten plants with analgesic and anti-inflammatory properties. Hardy and her colleagues have found evidence that Neanderthals ate yarrow and chamomile: plants that have medicinal uses but no nutritional value.

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