Abstract
Over the last few decades, comparative biology of aging has aimed toidentify factors responsible for the huge variability in lifespan observedacross the animal kingdom. While these studies have undeniablyimproved our understanding of the complex processes that shape lifespan,we argue that time has now come to focus on specific aging metrics (e.g.,age at the onset of aging, rate of aging) rather than on lifespan. Such a shiftin research programs would help decipher the fine-scale mechanismsshaping age-specific mortality profiles across the tree of life