The study of early hominin technology relies heavily on the analysis of stone tools, as wood artifacts rarely survive due to the challenging preservation conditions required. This scarcity of preserved wooden artifacts limits our understanding of when and how early hominins utilized this crucial material. This research addresses this gap by presenting evidence from Kalambo Falls, Zambia, which provides the earliest known example of structural wood use in the archaeological record. The discovery challenges the prevailing narrative of early hominins as primarily mobile foragers with limited technological capabilities. Understanding the extent and sophistication of woodworking during the Early Stone Age is critical for reconstructing early hominin behaviors, cognitive abilities, and their adaptation to diverse environments. The use of wood for construction implies a level of planning and cooperation exceeding previously assumed capacities, significantly impacting our understanding of early human social organization and technological innovation. The exceptional preservation at Kalambo Falls, due to waterlogged conditions, offers a unique opportunity to analyze wooden artifacts and reconstruct aspects of early hominin life that are otherwise inaccessible.

Previous evidence for woodworking in the Early Stone Age is scarce and often indirect. While use-wear traces and residues on stone tools suggest the processing of wood in East Africa during the Early Pleistocene, actual wooden objects are exceptionally rare. A polished wooden plank from Gesher Benot Ya'aqov, Israel, dated to over 780,000 years ago, represents the oldest known wooden artifact, but its use is unclear. Wooden tools, including spears and throwing sticks, appear in the Middle Pleistocene record of Europe and China around 400,000 years ago, with some possible evidence in Africa. Earlier work at Kalambo Falls uncovered wood artifacts, but taphonomic processes obscured evidence of intentional shaping. Other sites in southern Africa, such as Amanzi Springs and Florisbad, have yielded minimally modified wood pieces, but their dating and contexts are less secure compared to the Kalambo Falls discovery. The current study significantly advances our knowledge by providing direct and securely dated evidence for complex woodworking at an unexpectedly early date.

Excavations at Kalambo Falls in 2019 targeted site BLB, focusing on sediments above and below the river level. Sixteen sand samples were collected for luminescence dating, employing both single-grain quartz optically stimulated luminescence (OSL) and postinfrared infrared stimulated luminescence (PIR IRSL) from potassium-rich feldspars, to establish the chronological framework of the site. The wood artifacts were identified to species level using standard wood identification techniques. Radiocarbon dating attempts yielded infinite ages (over 50,000 years ago), confirming the great age of the artifacts. Infrared spectroscopy analysis investigated the degree of wood mineralization. Given the waterlogged nature of the artifacts, photogrammetry and reflectance transformation imaging (RTI) were used to overcome challenges associated with conventional imaging techniques. The manufacture marks and use history were documented using standardized terminology, and interpretations were supported by replication experiments. Functional interpretations were drawn from comparisons with waterlogged Holocene sites in Zambia, the UK, and ethnographic sources. Detailed descriptions of each artifact, including surface modifications, were provided and their functional interpretations are discussed.

The key finding is the discovery of two interlocking logs (object 1033, *Combretum zeyheri*) in excavation unit BLB5, securely dated to at least 476 ± 23 kyr ago. These logs are joined by a U-shaped notch, intentionally created through scraping and adzing. This structure exhibits no known parallel in the early archaeological record, representing the earliest evidence of structural wood use. The analysis of object 1033 reveals extensive intentional modification, including chopping and scraping marks on both logs. In the same unit (BLB5), Acheulean artifacts (flake tools, cleavers, and handaxes) were also found, associating the wooden construction with a well-established lithic technology. Further, the research uncovered four additional modified wood objects from units BLB2, BLB3, and BLB4, with ages ranging from 390,000 to 324,000 years ago. These included a wedge (object 660, *Kigelia africana*), a digging stick (object 219, *K. africana*), a cut log, and a notched branch. These findings demonstrate an unexpected diversity of woodworking techniques and forms during the Middle Pleistocene.

The findings significantly expand the temporal and technological scope of woodworking in Africa, demonstrating the capabilities of Middle Pleistocene hominins to not only create individual tools but also to construct complex structures from wood. The intentionally notched logs in BLB5 represent a significant advance in woodworking technology, implying advanced planning and cooperative effort in their construction. The presence of both lithic and wooden artifacts suggests a complex interaction between these materials and technologies in the early hominin toolkit. The age of the Kalambo Falls findings pushes back the known use of woodworking significantly. The ability to construct large wooden structures has implications for understanding early hominin settlement patterns, social organization, and adaptation to diverse environmental conditions. The findings challenge prevailing models of early hominin technology, cognitive abilities, and social structures.

This research reveals the earliest known instance of structural woodworking, pushing back the established timeline of this technology by a considerable margin. The discovery of intentionally modified wooden structures and tools at Kalambo Falls provides compelling evidence for the advanced technological and cognitive capabilities of Middle Pleistocene hominins in Africa. Future research should focus on exploring similar waterlogged sites across Africa and elsewhere to expand the limited record of early wooden artifacts and to better understand the development of woodworking technology during the Pleistocene.

The study is limited to the specific conditions of preservation at Kalambo Falls. The exceptional preservation of wood due to waterlogging is not typical of most archaeological sites, potentially leading to an underrepresentation of woodworking in the archaeological record. The interpretation of some artifacts relies on comparisons with later examples and ethnographic analogies, which may not be perfect matches. Future discoveries in other sites are needed to further evaluate the generality of the findings presented in this study.