Evidence for the earliest structural use of wood at least 476,000 years ago

The study addresses when and how early hominins used wood, focusing on identifying the earliest structural application of wood in the archaeological record. Because wood rarely preserves without exceptional conditions, knowledge of Early Stone Age woodworking has been sparse and often inferred indirectly from lithic use-wear and residues. Kalambo Falls, Zambia, offers waterlogged deposits that preserve wood. The purpose is to document, date, and interpret wooden artefacts and constructions from this site to reassess the technological capabilities and cognitive skills of Mid-Pleistocene hominins. Establishing structural use of wood would indicate advanced planning, tool use, and potential creation of built environments far earlier than previously recognized, thereby expanding our understanding of early technological diversity and cognition.

Indirect evidence for Early Pleistocene woodworking in Africa comes from use-wear and residue analyses on stone tools from Oldowan and Acheulean contexts in East Africa. Actual wooden objects are rare but occur in Mid-Pleistocene waterlogged deposits. Previous Kalambo Falls excavations (1950s–1960s) recovered wood from Acheulean horizons (sites A and B), though taphonomic processes obscured intentional shaping on most pieces; some notched objects suggested modification, but earlier dating attempts yielded only minimum ages. Other southern African sites include Amanzi Springs (Acheulean, ~404–390 ka) with wood but little evidence of modification, and Florisbad (Middle Stone Age) with a modified wooden fragment associated with hominin remains, though stratigraphic relationships to dated deposits are uncertain. Outside Africa, the earliest known wood artefact is a polished plank from Gesher Benot Ya'aqov (>780 ka). Wooden hunting/foraging tools are known from Europe (e.g., Schöningen), China (Gantangqing), and possibly Africa around 400 ka. This body of work indicates woodworking was present but left a sparse and often ambiguous record, with no previously known structural wooden constructions from the African or Eurasian Palaeolithic.

- Site and stratigraphy: Excavations in 2019 at Kalambo Falls, Zambia, focused on site BLB with units BLB1–BLB5. The Quaternary sequence is a ~9 m exposure above the Kalambo River comprising fluvial sands and gravels with discontinuous fine sands, silts, and clays. A permanently elevated water table preserved wood and plant remains, particularly in the lowermost ~2 m. The depositional environment was a high- to moderate-energy sandbed river with lateral migration; wood could be emplaced anthropogenically or naturally transported and snagged. - Sampling and dating: Sixteen sand samples (KF01–KF17) were collected for luminescence dating from deposits bracketing key finds, including those containing wood. Younger samples were dated using single-grain quartz optically stimulated luminescence (OSL); older samples employed post-infrared infrared stimulated luminescence (pIRIRSL) on K-feldspars, following robust protocols to minimize issues (e.g., fading, TT-OSL-related uncertainties). Ages cluster into three groups: 476 ± 23 kyr (lower deposits below river level: BLB3, BLB5), 390 ± 25 kyr (BLB2, above river), and 324 ± 15 kyr (BLB4, above river). - Wood identification and dating checks: Wood specimens were identified to species level where possible. Radiocarbon dating was performed to test for intrusive younger materials; all results were infinite (>50 ka), supporting antiquity. Infrared spectroscopy indicated partial mineralization (silicification) and offered indeterminate evidence for possible fire use in shaping. - Documentation and imaging: Because wood had to be kept wet, standard photography, structured light scanning, and microscopy were impractical due to reflectance and water pooling. Instead, photogrammetry and reflectance transformation imaging (RTI) were used on submerged specimens. Additional photographs were captured during brief drying periods. Surface modifications were recorded and analyzed on photographically generated models. - Analytical framework: Manufacture marks and use history were described using standardized wood-technology terminology, with interpretations supported by replication experiments. Functional interpretations drew on analogies from waterlogged Holocene sites in Zambia and the UK and ethnographic sources. Species identifications included Combretum zeyheri, Kigelia africana, and Ficus spp.

- Earliest structural wood construction: Two interlocking logs were found in BLB5 in basal sands with Acheulean artefacts (flakes, cleavers, handaxes). The upper log (object 1033; Combretum zeyheri) is 141.3 cm long and 25.6 cm wide with tapered ends, lying at ~75° over a larger underlying treetrunk. A U-shaped transverse notch (13.2 cm long × 11.4 cm wide) was intentionally cut into the upper log; the underlying modified trunk passes through this notch, forming a joined unit. Multiple chopping, scraping, and convex-shaping facets were documented around and within the notch, on the log surfaces, and on the underlying trunk. Imaging revealed intersecting linear striations with V-shaped cross-sections, entry facets, stepped facets, and areas of convex shaping. This is interpreted as an intentional join, creating a composite construction—unparalleled in the African/Eurasian Palaeolithic—and dated by bracketing sediments to a mean age of 476 ± 23 ka. - Additional wooden artefacts across age clusters: • BLB3 (lower cluster, ~476 ± 23 ka): Two objects among plant material with Acheulean tools. Object 660 (Kigelia africana), length 36.2 cm, rounded on one side with bark retained, tapers to an offset point cut ~60° across the long axis; displays convex facets and V-shaped striations near the tip and evidence of high-impact compression. Interpreted as a wedge/portable work base/incompletely processed firewood (function uncertain but intentionally shaped). Object 661 (Ficus spp.) is a V-shaped branch fragment with lenticular cross-section and no visible shaping marks (not modified). • BLB2 (intermediate cluster, 390 ± 25 ka): Object 219 (K. africana), two refitting parts totaling 62.4 cm length; base max breadth 11.9 cm, midsection 6.1 cm, offset tip 1.3 cm; concave upper surface without bark; faint transverse striations and small convex facets near the tip and around knots; interpreted as a digging stick based on morphology and facets. • BLB4 (upper cluster, 324 ± 15 ka): Two objects in clays without stone tools. The upper object (C. zeyheri) is a rectangular cut log (59.24 × 29.34 × 7.7 cm) with bark traces and sapwood exposed; shows radial cellular compression from overburden and distinct stepped chop marks across both ends, consistent with a broad, sharp cleaver-like cutting edge applied with direct force (handheld or hafted). Interpreted as a portion of treetrunk cut to size, indicating capacity for large-scale wood working. The lower object (C. zeyheri) is a tapered branch piece, length 37.9 cm (base 12.3 cm wide to broken tip 2.1 cm), bearing a single transverse V-shaped chop mark above the tip; function not determined. - Age structure and preservation: Luminescence ages are stratigraphically consistent (with a small exception between KF10 and KF11) and form three coherent clusters that bracket the wooden artefacts. Radiocarbon ages are infinite (>50 ka), supporting antiquity. Partial silicification and exceptional waterlogged preservation allowed detailed surface modification analyses. The assemblage shows early diversity of wooden tool forms and techniques, including scraping, adzing, chopping, convex faceting, and joining.

The findings directly address the question of early structural use of wood by demonstrating a deliberately engineered joint between two logs dated to at least 476 ± 23 ka. This composite construction evidences planning, controlled shaping, and the cognitive ability to combine parts into a functional unit—attributes linked to advanced technical cognition. The presence of cut-to-size logs, a probable digging stick, and a shaped wedge further shows a broader technological repertoire than inferred from lithics alone. The results illuminate co-evolution between Acheulean large cutting tools and woodworking tasks such as felling, hewing, and joint-making. Environmental context—a forested Kalambo River basin with a permanently elevated water table between ~470–274 ka—would have provided abundant timber and conditions conducive to repeated occupation. In such an environment, constructions like raised platforms, walkways, or foundations for dwellings could have enhanced habitation in periodically wet floodplains. The BLB5 interlocking logs also conceptually anticipate hafting (joining components into a single functional unit), suggesting that combining materials and parts was within the cognitive and technical scope of Mid-Pleistocene hominins. Overall, the study expands the recognized technological diversity and built-environment capabilities of hominins traditionally seen as highly mobile foragers with limited woodworking.

This study documents the earliest known structural use of wood: a pair of interlocking, intentionally joined logs from Kalambo Falls dated to at least 476 ± 23 ka. Alongside additional modified wooden artefacts spanning ~390–324 ka (wedge, digging stick, cut log, and an unassigned tapered piece), the assemblage reveals unexpected diversity in woodworking techniques and functions, including large-scale shaping and joint construction. These findings extend the temporal range of woodworking in Africa, demonstrate sophisticated technical cognition, and compel a re-evaluation of the role of trees and wood in early technological systems. Future research could target: (i) systematic surveys and excavations of waterlogged contexts to recover organic technologies; (ii) expanded luminescence dating frameworks for better chronological resolution; (iii) advanced non-invasive imaging to document ephemeral surface modifications; (iv) experimental replication and tribological studies to refine tool-mark interpretations; and (v) broader regional comparisons to assess variability in Mid-Pleistocene woodworking and its relationship to lithic technologies and emerging hafting practices.

- Preservation bias: Exceptional waterlogged conditions at Kalambo Falls enabled survival of wood; such contexts are rare, limiting generalizability across regions and time periods. - Documentation constraints: The need to keep specimens wet impeded standard photography, scanning, and microscopy. Some surface features degraded during storage, reducing definition of facets and marks. - Functional uncertainty: For some items (e.g., BLB3 wedge object 660, BLB4 lower tapered piece), functional interpretations remain tentative or indeterminate. - Dating nuances: While luminescence ages are stratigraphically coherent overall, there are minor exceptions (e.g., KF10 vs. KF11). Radiocarbon only provided infinite ages (>50 ka), offering no fine-grained absolute ages for the wood itself. - Taphonomic overprint: Earlier Kalambo materials suffered taphonomic modification, and even in 2019 finds, sediment compression and surface pitting affected interpretability of tool marks. Evidence for fire use in shaping is indeterminate.