The Ancient Antibiotic Hiding in Neanderthal Glue

About 50,000 years ago, a Neanderthal sat by a fire burning birch bark, patiently collecting the black, sticky residue that dripped onto a flat rock held above the flames. That tar would become the adhesive that secured a spear point to its shaft. But here's the thing: the same substance was also fighting off infection.

A team led by researchers at the University of Cologne and the University of Oxford has demonstrated what Indigenous peoples have known for millennia: birch tar works as an antiseptic. Their findings, published in PLOS ONE, confirm that Neanderthals didn't just stumble into a useful adhesive—they had access to a rudimentary antibiotic.

The Mi'kmaq of eastern Canada call it maskwio'mi. They prefer the more fluid version for wound dressings and skin ointments. The Saami and the Yakut have their own names for it too. These aren't recent discoveries. They're traditional knowledge passed down through countless generations. What the research team has done is explain the science behind why it actually works—and, in doing so, they've stumbled into a much bigger story about what Neanderthals were capable of.

How the Research Was Done

To test birch tar's antimicrobial properties, the researchers gathered bark from birch species already found at Neanderthal archaeological sites. They tested several extraction methods, ranging from the brutally simple to the more controlled.

Simple Method

Burn bark under a flat rock, collect the drippings — the method Neanderthals likely used.

Controlled Method

Heat bark in a clay vessel buried in a dirt mound — a more controlled approach.

The resulting substance ranges from an oily fluid to a brittle, tarry resin depending on how long it's heated in open air.

What the Tests Revealed

Against Staphylococcus aureus

Birch tar delivered solid results against S. aureus—the bacterium behind skin infections and the antibiotic-resistant MRSA strain. It either stopped the bacteria entirely or significantly slowed its growth, depending on which tree species the bark came from and how concentrated the tar was.

Silver birch, Betula pendula, produced the strongest response. Other species ranged from mild to moderate in effectiveness, and one had no measurable impact.

Against E. coli

E. coli, however, walked away untouched. That outcome wasn't surprising to the researchers: Gram-negative bacteria like E. coli possess an outer membrane that can block antimicrobial compounds—a barrier Gram-positive bacteria like S. aureus lack.

The Active Ingredients

The researchers identified likely culprits behind birch tar's germ-fighting power:

Phenolic derivatives — Ring-shaped molecules common in antiseptics and surgical skin cleansers.

Terpenes and terpenoids — Compounds that help plants fend off insects and fungal infections.

It's the same logic as DEET-based repellents against mosquitoes—only Neanderthals discovered it without a chemistry degree.

Of course, the tar is nowhere near as potent as modern antibiotics. Gentamicin clobbered S. aureus far more effectively than any birch tar sample. That's like comparing a fire hose to a squirt gun.

But the point isn't that Neanderthals had pharmaceutical alternatives—it's that they possessed enough empirical knowledge to make informed choices about which materials did what. They may not have understood crystallography or atomic structures, but they knew their materials.

A Messy Clinical Trial

Neanderthals were distilling birch tar by 200,000 years ago. The residue on a stone flake pulled from the North Sea tells us that by 50,000 years ago, this process was routine—efficient enough to be worth the effort, which requires careful control of temperature and oxygen levels. Generations of experimentation refined the method into something repeatable.

Here's the part the research team finds almost endearing: the tar gets everywhere. Its low viscosity when produced in underground pits, combined with its adhesive properties, means skin contamination during handling is essentially unavoidable. About 2 grams can cover up to 100 square centimeters of skin.

The researchers noted that getting the tar off their hands after hours at the fire was "a challenge every time."

That messiness may have been the original clinical trial. Scratch an itchy patch, drip tar on an open wound, notice the redness subsiding—repeat for a few thousand years and you've got empirical medicine.

The same logic applies to ochre, which appears in Neanderthal sites alongside evidence of sunscreen use and possibly wound dressings. These weren't just aesthetic choices. They were functional ones.

A Broader Pattern Emerges

We already knew Neanderthals used chamomile and yarrow—chemical traces remain in the dental calculus of specimens from El Sidrón in Spain and Shanidar in Iraq. Both plants contain compounds useful as anti-inflammatories and digestive aids.

Add birch tar to the list, and a picture emerges of hominids who were keen observers, capable of working through cause and effect across generations.

The findings reinforce what past studies have reported and echo traditional knowledge. The research also hints that this particular piece of traditional knowledge might be far older than even oral histories record—or that similar discoveries were made independently, again and again, by people who watched carefully and learned from what they saw.

This isn't definitive proof that Neanderthals were running a prehistoric pharmacy. But it demonstrates what they could have done, which means we now know what to look for. And that's exactly how science works: one messy, tar-covered experiment at a time.

Based on: Ancient Antibiotics: Birch Tar as an Effective Antimicrobial; Siemssen T. et al.; PLOS ONE, 2024.