In "A Short History of Nearly Everything," Bill Bryson discusses the importance of external signals for cellular survival. He notes that cells are not self-sufficient entities; instead, they require guidance and instruction from their environment to continue functioning. Without these signals, cells tend to undergo programmed cell death, demonstrating their dependency on external factors for sustenance and motivation.

This observation highlights the intricate nature of life at the cellular level, where reassurance from surrounding conditions shapes cell behavior. Bryson's insight reveals the complexities of biological systems, illustrating how even the simplest life forms rely on communication and support to thrive, underlining the interconnectedness of life in a broader sense.