On Comparative Longevity in Man and the Lower Animals. This item is unavailable.On Comparative Longevity in Man and the Lower Animals

On Comparative Longevity In Man And The Lower Animals by Edwin Ray Lankester. This monograph, originally published in 1870, surveys how lifespan varies across life forms, from protozoa to mammals, and analyzes the factors shaping longevity. Lankester distinguishes three kinds of longevity: normal potential longevity, absolute potential longevity, and average longevity, and argues that high individuation (complex structure and development) and low personal and generative expenditure tend to extend life, while high expenditure shortens it. Drawing on Bacon, Flourens, Spencer, and contemporary data, the essay formulates a general law: longevity is favored by high individuation and by low expenditure, and is moderated by environmental factors (milieu) and heredity. The work also applies these concepts to humans in different states of civilization, noting how social organization, nutrition, climate, and cultural practices influence life expectancy, and discusses the limits and possible future trajectories of human longevity. It includes inductive evidence, proposed life tables, and a broad discussion of the nature of life, death, and senescence across life forms.