Abstract
Comparative biology plays a crucial role in uncovering fundamental biological mechanisms and providing evolutionary models for their variation. This approach is particularly valuable for studying aging, given the remarkable diversity in aging trajectories across the tree of life. Many evolutionary theories of aging were proposed well before the discovery of the molecular mechanisms involved, and they remain largely theoretical. Moreover, the growing number of model organisms and the expanding array of experimental and theoretical approaches used to study aging have often remained compartmentalized. As a result, integrating these diverse insights into a unified framework has become increasingly important. As a step toward this goal, this field perspective outlines general biological mechanisms that help explain the variability in aging patterns and longevity across the animal kingdom.