Longevity is one of the most variable life history traits among animals, ranging from days (e.g. adult mayflies) to centuries (e.g. the Greenland shark). Based on this variability, claims that some species display exceptional longevity are regularly published. Yet determining whether a species shows exceptional longevity or not is far from an easy task. For instance, longevity is (among other traits) associated with body mass, according to an allometric relationship, and a species displaying exceptional longevity should typically break this relationship. Longevity also corresponds to a biological time measuring the speed of the life cycle (often called pace of life) and should be isometrically linked with other biological times such as developmental time or age at first reproduction. From that perspective, a species displaying exceptional longevity should break these relationships as well. However, how much the observed longevity should differ from the predicted values for a given body mass or a given pace of life to be labelled as exceptional is fuzzy. Similarly, what is the threshold age at which a set of individuals displaying exceptional longevities can be identified? The aim of this chapter is to provide a critical reappraisal of some statistical methods used so far to determine whether a species or an individual shows exceptional longevity and then to provide a clear roadmap to identify such species and individuals. The analyses presented in this chapter are based on demographic databases on mammals and some exceptionally detailed case studies (on medflies, rhesus macaques and mole rats) at the individual level.

Life history theory has revolutionized the study of the evolved life course both across and within species. Humans are no exception. Life history theory provides nuance to claims of human uniqueness in the tree of life, including among mammals, and among primates in particular. This chapter first explains how life history theory delivers optimal trait characteristics given trade-offs that are defined by costs and benefits of different “solutions” to fitness-relevant problems. It reviews the current understanding of the evolution of the human life course, and the chapter evaluates explanations of long postreproductive life spans in human populations. It then provides a framework for modeling how selection pressures in different socioecological settings could shape the flexible expression of demographic, physiological, and even psychological traits in our species. Special emphasis is placed on the role that exogenous mortality and environmental unpredictability (and their cues) play on shaping a number of behavioral and physiological traits related to survival. Claims certainly outpace definitive tests, but after a half century, since life history theory was first introduced to the human life sciences, promising new directions are expanding the breadth of topics covered beyond demography, using multiple methods and spanning diverse disciplines.