Paleodemography looks at the changes in pre-modern populations in order to determine something about the influences on the lifespan and health of earlier peoples. It is the field of inquiry that attempts to identify demographic parameters from past populations (usually skeletal samples) derived from archaeological contexts, and then to make interpretations regarding the health and well-being of those populations. Reconstruction of ancient population sizes and dynamics are based on bioarchaeology, ancient DNA as well as inference from modern population genetics. This is important, as it is not always obvious how many bodies compose the bones sitting in a heap as they are excavated.