The floor of Niah's Great Cave is an archive. Beneath the current surface lies a sequence of sediment layers — each containing organic remains, stone tools, animal bones, charcoal, and human burial goods — that records occupation of the site from at least 60,000 years BP to the historic era. Reading this stratigraphy is like reading a book where each page is a different century, but the pages are compressed to millimetres and written in the language of chemistry and decay rather than words.
Tom Harrisson's excavations in the 1950s–60s identified the major cultural horizons. At the base: flaked stone tools associated with the Deep Skull and contemporaneous fauna including extinct mammals and birds. Moving upward through the stratigraphy: the Hoabinhian cultural layer from approximately 10,000–5,000 BP, characterised by distinctive sumatralith stone tools; a Neolithic layer from 4,000–2,000 BP with polished stone tools, hand-coiled pottery, and the first evidence of cultivation; and the Metal Age layer from 2,000 BP to the historic era, with iron tools, glass beads, and Chinese trade ceramics.
The depth and completeness of this sequence is unusual even by global standards. Most of the world's major prehistoric sites offer a few hundred or at most a few thousand years of occupation record. Niah's 60,000-year archive is exceptional, and the relative dryness and chemical stability of the guano-rich cave sediment has preserved organic materials — bone, plant remains, charcoal — that would not survive in open-air sites in the tropics. Recent uranium-series dating of stalactite overgrowths on excavated artefacts has allowed far more precise chronology than the original radiocarbon dating permitted.
The Sarawak Museum and the Niah Archaeological Project (a collaboration between the University of Cambridge and Malaysian institutions) are conducting ongoing excavations using modern stratigraphic and environmental science methods. Results from the most recent fieldwork (2018–2024) are revising the occupation sequence and pushing some horizon dates earlier than Harrisson's original estimates. The park's visitor centre displays a cross-section model of the main excavation trench and explains the stratigraphic column with artefacts from each layer. The Painted Cave completes the cultural picture — the boat-of-the-dead paintings represent the most recent prehistoric cultural expression at the site, sitting at the top of the same long stratigraphic record.