Making our way into this world, we face a string of challenges: the conceptus must implant in the uterus and within the next nine months develop into a fetus strong enough to survive the struggle of birth and the separation from the mother’s organism. Having made this transition, the newborn’s resilience against death continues to be tested: it needs to learn to fight infections, to digest food, and to communicate basic needs while remaining entirely dependent on appropriate care. But each challenge overcome is rewarded by a better prospect of future survival. From conception until maturity, the hazard of death declines continuously – only disrupted by the event of birth. While human life has famously been characterized as a “being-toward-death” (Heidegger 1962), the situation initially is reversed: With each additional day of survival, the child moves further away from death. The phenomenon of declining rates of mortality between conception and maturity has been coined “ontogenescence” (Levitis 2011). This thesis concerns its quantification.