Matthew Ward Agius
Matthew Agius is a science writer for Cosmos Magazine.
Pulling two joined logs from the ground might ordinarily be an unremarkable event, but for British archaeologists working in Zambia, their recent discovery marks the oldest evidence of human construction – predating the emergence of our own species, Homo sapiens.
The findings were made after excavating a site near Kalambo Falls in Zambia as part of a University of Liverpool (UK) project charting early technology used by early humans 500-300,000 years ago.
They believe the two highly preserved wooden logs were joined to form the foundation of a shelter or platform. The wood was taken to Aberystwyth University in Wales for luminescence dating, and found to be about 476,000 years of age – a particularly ancient structure considering the first H. sapiens emerged about 100,000 years later.
While wood rarely lasts for such extensive periods, the high-water levels at Kalambo preserved the specimens until they were dug up recently.
And while similar specimens had been recovered from the same location six decades ago, the measurement techniques and technology required to accurately date them had only been available after those specimens were uncovered.
“At this great age, putting a date on finds is very challenging,” says Professor Geoff Duller, an expert in luminescence dating at Aberystwyth University.
“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. 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.”
Luminescence dating is used to determine the age of a material like quartz by measuring the last time it was exposed to sunlight. In such cases, the accumulated energy absorbed by the material’s exposure to radiation from radioactive isotopes over timescales of tens and hundreds of thousands of years. When a material is exposed to sunlight, the energy stored over these periods is ‘reset’ and the release of this stored energy is used to calculate the object’s age. When a material – such as wood – might not be suitable for luminescence dating, the sediments surrounding it can be used as a proxy.
The discovery represents the first evidence of wooden logs being purposefully connected to create large structures, rather than simple spears, digging sticks or fire-making tools. The finding, says study lead Professor Larry Barham from the University of Liverpool, challenges assumptions of early human technology and lifestyle: at a place like Kalambo, ancient people had access to water and wood to help them settle in a single location, rather than moving from place-to-place as had often been assumed.
“Forget the label ‘Stone Age,’ look at what these people were doing,” says Barham, “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.”
As a result of the findings, Barham and Duller have added their voices to calls for Kalambo Falls to be recognised as a World Heritage Site.
“Our research proves that this site is much older than previously thought, so its archaeological significance is now even greater,” says Duller.
