Which type of system cannot evolve to be simpler without losing functionality?

An irreducibly complex system is characterized by the interdependence of its parts, meaning that all components must be present and functioning together for the system to operate effectively. If any part is removed or simplified, the entire system loses its ability to perform its intended function. This concept is often discussed in the context of biological systems, such as certain molecular structures or biochemical pathways, where each component plays a critical role that cannot be replaced or omitted without rendering the entire system nonfunctional.

In contrast, modular systems can often be reconfigured or simplified by removing or altering certain modules while still retaining overall functionality. Hierarchical systems are structured in layers or levels that can be reorganized without necessarily diminishing their functionality. Scalable systems can adjust in size or capacity, maintaining their effectiveness as they expand or contract. Therefore, the principle behind irreducible complexity is fundamental to understanding why simplification is not an option without losing essential functionality.