The excavation team uncovering the wooden structure. Credit: Larry Barham, University of Liverpool
Using a new, more accurate dating technology, researchers have found and confirmed the world’s oldest wooden structure—the earliest evidence from anywhere in the world of the deliberate crafting of logs to fit together.
The structure, probably the foundation of a platform or part of a dwelling, dates back at least 476,000 years, predating the evolution of Homo sapiens. This is half a million years earlier than was previously thought possible.
The excavation of the well-preserved wood occurred at the archaeological site of Kalambo Falls, Zambia. Wood is rarely found in such ancient sites as it usually rots and disappears, but the permanently high water levels of Kalambo Falls acted as the perfect preservation tool for the wood.
Until now, evidence for the human use of wood was limited to making fire, digging sticks and spears. But, expert analysis of the wood found at Kalambo Falls clearly shows stone tool cut-marks on the wood where early humans shaped and joined two large logs to make a structure, the researchers say.
“This find has changed how I think about our early ancestors,” said study author Larry Barham, from the University of Liverpool. “Forget the label ‘Stone Age,’ look at what these people were doing: they made something new, and large, from wood. They used their intelligence, imagination, and skills to create something they’d never seen before, something that had never previously existed. They transformed their surroundings to make life easier, even if it was only by making a platform to sit on by the river to do their daily chores. These folks were more like us than we thought.”
Wooden remains
In 2019, archeologists recovered five “modified” wood objects from a specific site at Kalambo Falls, both above and below river level.
One of the objects (excavation pictured above) is a log about 141.3 cm long × 25.6 cm, with tapering ends in three parts. The log overlies a larger tree trunk at a 75° angle. The area of overlap is a U-shaped notch, transverse to the long axis. The underlying log, which had also been modified, passes through a central notch cut into the upper log and extends into the section. The research team believes this was built as the foundation of a platform—perhaps to sit on—or as part of a dwelling.
Another object is rectangular with wood exposed on the longitudinal surfaces. The researchers found well-preserved chop marks at the end, where they descend in four steps, with a V-shaped profile.
“The length of cuts and slight curvature suggest a broad, sharp, cleaver-like edge, the depth indicating applied direct force, either handheld or hafted,” the researcher explain in their paper. “We interpret this object as a portion of tree trunk cut to size, indicating capacity to work wood at a large scale.”
While sticks and spears have been recovered previously, the research team believes they may have found a wedge. This object is rounded on one side with outer bark on both surfaces, before it tapers to an offset point cut 60° across the long axis. In addition to a wedge, the researchers say it could be incompletely processed firewood and a portable work base.
Accurate dating
Sixteen samples of sand for dating were collected surrounding the site of the recovered wood by hammering opaque plastic tubes into the sediment. A combination of field gamma spectrometry, laboratory alpha and beta counting and geochemical analyses were used in the dating process. But the innovative change was the use of new luminescence dating techniques—which reveal the last time minerals in the sand surrounding the finds were exposed to sunlight in order to determine their age.
“These new dating methods have far-reaching implications, allowing us to date much further back in time, to piece together sites that give us a glimpse into human evolution,” said study author Geoff Duller from Aberystwyth University, where the dating analysis took place. “The site at Kalambo Falls had been excavated back in the 1960s when similar pieces of wood were recovered, but they were unable to date them, so the true significance of the site was unclear until now.”
That particular finding helps, as the area is on a “tentative” list from UNESCO for becoming a World Heritage site because of its archaeological significance.
“Our research proves that this site is much older than previously thought, so its archaeological significance is now even greater. It adds more weight to the argument that it should be a United Nations World Heritage Site,” said Duller.