World’s oldest wooden structure discovered in Zambia

The Stone Age can also be known as Wood Age, a fact that has become evident only recently. A remarkable discovery was announced by an international team in Nature magazine on September 20th. The discovery relates to the oldest wooden structure ever found, dating back a staggering 476,000 years to an era when modern humans had not yet emerged.

This remarkable find took place in northern Zambia, not far from the Kalambo River Falls. The site’s proximity to the river results in frequent flooding, which deposits sediment. It is this continuous moisture that enabled the preservation of the wooden artifacts, as explained by Veerle Rots, a prehistory professor at the University of Liège (Belgium) and a co-author of the study. The site was initially excavated in the 1950s by British archaeologists, yielding intriguing remains, although its dating was uncertain.

In 2019, a collaborative effort between the universities of Liverpool, Aberystwyth (United Kingdom), and Liège rekindled excavations at Kalambo Falls. Within the waterlogged sands, the team unearthed several wooden items, including a striking cruciform structure. This structure consisted of two logs positioned through a U-shaped notch, over 10 centimetres wide, clearly shaped by human hands, as evidenced by the marks left by stone tools on the wood.

However, a critical question remained: determining the era when this structure was constructed. Carbon-14 dating yielded no results, as it is limited to around fifty thousand years. To address this, the researchers turned to luminescence dating, a technique that enables the dating of sediments surrounding an object rather than the object itself.

This method relies on the ability of certain natural crystals, like quartz and feldspar, to act as dosimeters due to tiny structural defects that function as electron traps. When exposed to natural radioactivity, these crystals accumulate energy, which they release when heated or illuminated in a laboratory setting. Each exposure to sunlight resets these crystals’ “internal clock” to zero, and they begin accumulating energy again when in darkness, such as when buried in sediments. The stored energy is proportional to the time spent in darkness, allowing researchers to determine the time elapsed since the last exposure to light.

The discovery catapults us nearly half a million years into the past, raising questions about the potential purposes of this wooden structure. Veerle Rots cautiously suggests that its function is not entirely clear because only a fragment remains. One hypothesis posits that it could have been used in wetlands, where humans constructed platforms to stay dry during river floods. This finding also challenges the notion of entirely nomadic populations, suggesting that they might have structured habitats or frequented specific areas regularly.

As for the identity of the creators of this structure, it predates the oldest known Homo sapiens by 300,000 years, with the possibility of being associated with archaic humans or Homo heidelbergensis. However, given the presence of multiple human species in Africa during that time and the absence of anatomical remains at Kalambo Falls, definitive identification remains challenging, especially in humid contexts that are less conducive to bone preservation.

In addition to the cruciform structure, the study unveiled other wooden elements and tools, dating between 324,000 and 390,000 years old. These include what researchers interpret as a wedge, a burrowing stick with a point, a log, and a notched branch. While these findings are less surprising, as similar examples have been discovered before, such as the 300,000-year-old spears in Schöningen, Germany, in the 1990s, they enrich our understanding of prehistoric technologies that relied on perishable materials.

For historians, the Kalambo Falls discovery is groundbreaking, showcasing the cognitive abilities and skills of our ancestors or their relatives. It underscores the innovation and resourcefulness of ancient people, who demonstrated capabilities that were previously unimaginable for such remote periods. They used their intelligence, imagination, and skills to create something entirely new, something that had never existed before. This suggests that these ancient people were more similar to us in their abilities and activities than previously believed.