There are grounds to suspect the existence of various human aging syndromes, whose courses have individual and populational features. The species-specific features of aging are related to the life-span of a species. Four types of indices have been identified in the studies of aging patterns in different animal species: the indices changing with age; the chronological indices that change more if the life-span of an animal is longer; the ontobiological indices that undergo similar changes in animals with various life-spans; and species-specific indices. When postulating the general mechanisms of aging based on the changes in the indices peculiar to the animals of the same species, it is important to know whether the indices are universal or species-specific.