Aging is a topic of considerable importance in biological anthropology. The steady number of publications and their emphasis on method development, testing, and validation provides clear evidence of sustained interest, while the history of debate over the validity of this theoretical work and their practical outcomes is testament to the depth of our collective investment. There is no denying how the reliable estimation of age-at-death from the human skeleton is of fundamental importance for the value that it brings to the field, and subfields, of biological anthropology, and to the areas of specialty and subject matter with which it interacts. The study of age contributes to our understanding of morphological variation and the senescent process in modern population biology. As such, skeletal development and degeneration has implications that reach into the anatomical and medical fields as we, as skeletal biologists, can grapple with the effects of genetics, environment, and individual lifestyle factors on bone density, rates of fracture healing, and atypical skeletal expression. Estimating age is important among the personal identity parameters that are used in medico-legal case identification in forensic anthropology, as we seek to provide law enforcement, medical examiner, and nongovernmental agencies with the information that can help to link the unknown individual with the named person. In these circumstances, the anthropologist, working in the service of humanitarian aid and social justice, estimates skeletal age to assist in missing person, asylum seeker, and undocumented death cases. Finally, age-at-death is fundamental to the paleodemographic reconstruction of mortality profiles for skeletal assemblages in bioarcheology, allowing us to bring a better understanding of the life and death of past peoples.