Are pregnant mammals emergent substances?

Metaphysically, pregnant mammals are unique in that they are objects that generate new objects. Thus they are generative. In this work, I test whether pregnant mammals may therefore be emergent substances, on the grounds that their biological generativity renders them causally non-redundant. I proceed by first explaining substance emergentism, under which causally non-redundant objects are taken to be individuals, that is, mereological simples. 1 then adopt a metaontological framework for emergence that further clarifies its ontological commitments. With these in place, I consider whether three entities related to mammalian pregnancy—the blastocyst, the fetus, and the pregnant being itself—are theoretically accounted for as emergent substances. I consider the fetus and the pregnant being under two separate models of pregnancy that suggest a variable number of particulars to be present in a pregnancy because each model implies a different definition of generativity. I conclude that pregnant mammals interpreted in terms of the two available models lead to undesirable metaphysical conclusions. In light of the phenomenon of pregnancy, either the theory of substance emergence must be revised to allow for co-location, or both models of pregnancy must be rejected. I suggest that revising substance emergence is the wrong solution, and that both models should be rejected. Instead, we need a new way to theorize generativity and a new model of pregnancy. Pregnancy as a phenomenon should shift the terms in which discussions of numerical identity, qualitative identity, and mereology occur in metaphysics, assuming the goal is a metaphysics compatible with naturalism.