When did we begin to exist? Barry Smith and Berit Brogaard argue that a new human organism comes into existence neither earlier nor later than the moment of gastrulation: 16 days after conception. Several critics have responded that the onset of the organism must happen earlier; closer to conception. This article makes a radically different claim: if we accept Smith and Brogaard’s ontological commitments, then human organisms start, on average, roughly nine months after conception. The main point of contention is whether the fetus is or is not part of the maternal organism. Smith and Brogaard argue that it is not; I demonstrate that it is. This claim in combination with Smith and Brogaard’s own criteria commits to the view that human organisms begin, precisely, at birth.