Ending the Search: The 2024 Callao Cave Excavation

Armand Salvador B. Mijares* and Eleanor Lim

With the discovery and subsequent introduction of Homo luzonensis excavated from Callao Cave northeastern Luzon in 2019, a number of issues have risen. In order to address these issues, further excavation at Callao Cave would be required to recover more diagnostic fossil remains – skull, mandible, long bones. Based on previous excavations, a hydraulic hypothesis has been put forward to understand the depositional history of the fossils. Based on this hypothesis, materials from the breccia layer were deposited through a paleochannel flowing beside the eastern wall of the cave. The flow was initially identified to be northward flowing. During the 2024 excavation, two excavation units were set up south of the fossil area; no new Homo luzonensis fossil were recovered. This instigated the revision of the hypothesis to a southward flow of the channel. In 2025, four excavation units were set up in the second chamber, north of the fossil area. Again, no new Homo luzonesis fossils were recovered. The site deposition and post deposition history of the second chamber also warrants further discussion. Although most of the sedimentary layers found during the previous excavation of the ante chamber were observed, these layers had undergone intense diagenesis. No or limited archaeological materials were also recovered in these layers. The team has now decided to terminate any further excavation at Callao Cave as the most probable areas that might contain fossils had been excavated.