The logs had notches carved into them and were found laying perpendicular to one another, suggesting they were designed to fit together.
A pair of prehistoric logs recently unearthed near Kalambo Falls in Zambia are believed to be part of the earliest known wooden structure on Earth. Now, researchers say this discovery is challenging long-held beliefs about the way early human ancestors lived.
While digging on the banks of the Kalambo River, archaeologists discovered a pair of wooden logs joined by a carved notch and lying on top of one another at a right angle.
“One is lying over the other and both pieces of wood have notches cut into them,” Geoff Duller, professor of geography at the University of Aberystwyth and a member of the team, told the BBC. “You can clearly see those notches have been cut by stone tools. It makes the two logs fit together to become structural objects.”
Larry Barham, an archaeologist at the University of Liverpool, led the Deep Roots of Humanity team on the Kalambo Falls excavation. Barham said he was baffled by the purpose of the logs, but then he remembered the U.S. building toy Lincoln Logs, according to an interview with Nature. Like the logs found in Zambia, Lincoln Logs are notched at the ends so the pieces can interlock, thus creating a stable structure.
The Kalambo logs appear to be part of a fixed platform. According to the team, the structure was unlikely to be a hut or any kind of dwelling. Researchers speculate it may have been part of a bridge, or the platform for some kind of shelter.
“It might be some sort of structure to sit beside the river and fish,” Duller said. “But it’s hard to tell what sort of [complete] structure it might have been.”
Dating on the logs showed the structure is an astonishing 476,000 years old — predating the evolution of Homo sapiens by more than 100,000 years.
“It could be a different species — [perhaps] Homo erectus or Homo naledi,” Duller said. “There were a number of hominid species around at that time in southern Africa.”
The find was shocking because researchers had long believed that such early human ancestors were nomadic and used wood only to make fire and craft tools. The fixed platform suggests they were less nomadic than previously thought.
“I was amazed to know that woodworking was such a deep-rooted tradition,” said team member Perrice Nkombwe from the Livingstone Museum in Zambia. “It dawned on me that we had uncovered something extraordinary.”
This discovery is even more remarkable considering how rare wood artifacts are in the archaeology world, given that wood decomposes much more quickly than materials like stone or iron.
Barham says it was the wet conditions at Kalambo Falls that allowed the logs to be preserved for nearly half a million years. The river’s waterlogged sediment prevented the wood from decomposing, and the wood also absorbed minerals from the water as time progressed, making it more durable.
It’s likely humans have been using wooden tools since a “long way back,” said Andy Herries, a paleoanthropologist and geoarchaeologist at La Trobe University. In Israel, archaeologists found a fragment of a polished plank that dated back 780,000 years, and a handful of other wooden artifacts found around the world date back approximately 300,000 years.
The logs found at Kalambo Falls were dated using a new technique called applied luminescence dating, according to Science. Buried minerals often absorb radioactivity and use it as energy. In the lab, the stored energy is released, and the minerals glow; the intensity of the glow indicates how long it has been since the mineral was exposed to sunlight.
The logs have been transported to the UK for analysis and preservation, but will soon be returned to Zambia for display.
“With this discovery, we hope to enrich our collection and use the finds to inform the interpretation of the woodworking tradition in Zambia,” Nkombwe said. “[The Kalambo Falls site] has the potential to deepen our knowledge of ancient woodworking techniques, craftsmanship, and human interactions with the environment.”
After reading about the 500,000-year-old wooden structure, read about the 7,275-year-old well that was previously the oldest known wooden structure. Or, read about the 300,000-year-old throwing stick that is among the oldest documented wooden tools made by humans.