Shell artefacts in Island Southeast Asia have often been considered local variants of ground-stone implements, introduced in the Late Pleistocene from Mainland Southeast Asia. The discovery of a well-preserved Tridacna shell adze from Ilin Island in the Philippines, suggests, however, a different interpretation. Using radiocarbon dating, X-ray diffraction and stratigraphic and chronological placement within the archaeological record, the authors place the ‘old shell’ effect into context, and suggest that shell technology was in fact a local innovation that emerged in the early Middle Holocene. The chronology and distribution of these artefacts has significant implications for the antiquity of early human interaction between the Philippines and Melanesia. It may have occurred long before the migrations of Austronesian-speaking peoples and the emergence of the Lapita Cultural Complex that are traditionally thought to mark the first contact.