The Bimin‐Kuskusmin of the West Sepik interior of Papua New Guinea elaborate a complex folk theory of procreation that becomes the ‘natural’ foundation of some ideologically significant constructions of the individual, the person, gender, and societal continuity. Drawing on certain aspects of Weiner's model of reproduction and regeneration, symbols of substance and insubstantial ‘spirit’ that form this ‘natural’ foundation of the Bimin‐Kuskusmin ideology of birth, death, and rebirth are explored in contexts of rites of passage that mark the course of the life‐cycle from conception to death and ancestorhood. The key symbols of this cultural ideology are the enduring substances of bone, bone marrow, andfiniikspirit, which are the basis of reckoning the cyclical regeneration o