In "Stiff: The Curious Lives of Human Cadavers," author Mary Roach explores the profound connection between our existence as biological beings and the inevitability of life and death. She highlights that we are consistently reminded of our biological nature from the moment we are born until we pass away. These milestones serve as reminders of our mortality and the physical aspects of being human.

Roach suggests that, throughout our lives, we often try to overlook our biological reality, focusing instead on daily distractions. However, these two pivotal moments—birth and death—bring us back to the truth of our existence. The book prompts readers to reflect on the importance of acknowledging our biological selves and how this awareness shapes our understanding of life.