Kalambo Falls

Kalambo Falls, where the Kalambo River plunges 235 metres in a single drop near the border between Zambia and Tanzania — among the highest uninterrupted waterfalls in Africa — has been an important archaeological site since excavations began in the 1950s, with sediment layers preserving an unusually long and well-stratified record of Stone Age tool use spanning hundreds of thousands of years, due to the waterlogged conditions that preserve organic material rarely surviving elsewhere in the archaeological record.

In September 2023, a team led by archaeologists from Liverpool John Moores University and Aberystwyth University announced the discovery, at a site near the falls, of two interlocking logs joined by a deliberately cut notch, forming part of what researchers interpreted as a structure — possibly a raised platform, walkway, or the foundation of a dwelling. Using a luminescence dating technique, which measures when mineral grains were last exposed to sunlight, the team dated the wood to approximately 476,000 years ago — roughly 400,000 years before the emergence of Homo sapiens, meaning the structure was built by an earlier human species, possibly Homo heidelbergensis. The find substantially predates the previous oldest known woodworking evidence and was unexpected because wood almost never survives from such early periods; the Kalambo find was preserved only because it had been permanently waterlogged in river sediments for nearly half a million years. The discovery has prompted researchers to reconsider assumptions about the technological and cognitive capabilities of pre-sapiens human relatives, who had previously been thought, on the basis of stone tools alone, to have led a more purely nomadic existence without constructed shelters.