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.

For decades, researchers have tried to identify ecological and biological correlates of longevity, often using life expectancy and maximum lifespan as the gold standards. The recent increase in demographic data collected in non-model species has also led researchers to develop alternative metrics of longevity, especially in comparative analyses (e.g. 90% longevity). As a result, studies focused on longevity rely on heterogeneous statistical methodologies and use a variety of longevity metrics that are not always clearly defined. This lack of clarity has led to confusion in the interpretation of results and makes it difficult to compare results across studies. This chapter discusses the statistical interpretation of each metric and highlights potential biases associated with the missus of longevity metrics; conducts a systematic review of the various longevity metrics used across the scientific literature and analyses the content of scientific articles on longevity using topic modelling methodology; and illustrates, using two examples, the importance of selecting the appropriate metric based on the research question. Based on these insights, it provides a list of recommendations aimed at helping researchers to think carefully about the choice of metrics when studying longevity.

The dream of eternal youth and immortality has always fascinated human societies. Even today, this quest is the source of major financial investments, particularly for the development of anti-ageing drugs. To unravel the mysteries of longevity, scientists have long been observing and quantifying the lifespan of animals. These decades of extensive comparative biology research have documented the extreme diversity of lifespan on Earth and identified key ecological and life history factors driving this diversity and, more recently, molecular pathways that might modulate it. However, the maximum lifespan of a species is far from being an accurate representation of a species’ ageing trajectory, both biologically and demographically. For a given species, the changes in mortality risk over the life course can be complex, and the ageing process is much more accurately described by ageing parameters, such as the age of onset of actuarial senescence and the rate of actuarial senescence. This chapter argues that current research in the comparative biology of ageing should now focus on the diversity of actuarial senescence patterns documented across the tree of life, as well as the species-specific causes of death, to identify key genetic and physiological determinants associated with delayed actuarial senescence or low actuarial senescence rate. Just a few years ago, such research projects would have seemed unrealistic, but the recent development of omics tools, coupled with the increased availability of demographic data for a wide range of species with contrasting life histories, lifestyles and habitats make such exciting comparative analyses now achievable and full of promise.

The demography of contemporary hunter-gatherers, farmers and other subsistence populations provides an important lens for studying age patterns of survival and morbidity under non-industrial conditions and lifeways. Although high-quality evidence is sparse, a review suggests robust patterns of human longevity that contradict prior notions of ‘nasty, brutish and short’ lifespans suggested from the palaeodemographic literature. Life expectancy at birth averages about 30 years for hunter-gatherers, and 35 years across all human subsistence groups, a pattern similar to mid-eighteenth-century Europe. Despite short life expectancy, subsistence populations show a modal adult lifespan of about seven decades across a wide range of environments, diets and livelihoods. Over a third of adult life is spent post-reproductive. Infection, violence and accidents are primary causes of death. Post-contact acculturation has mostly improved survivorship, especially in early life, due to access to health care and modern amenities. Loss of land and livelihood, new infections and exploitation, however, have increased mortality and morbidity in some populations. Although the past two centuries have witnessed large gains in lifespan equality and survivorship, the potential for human longevity appears to be a species-typical universal.

This opening chapter provides an overview of the future societal and subsequenl scientific challenges associated with population ageing. More specifically, it emphasizes how the field of biodemography constitutes a relevant framework for future research programmes aiming to address questions of paramount importance regarding both the causes (e.g. evolutionary, mechanistics) and consequences (demographic, medical) of the ageing process. Finally, this chapter details the book contents.

Solitude is unique to each person but there are patterns we have observed that we believe shed some light on what kinds of changes we should be aware of and what those mean for well-being in that space during different phases of our lives. Across the lifespan, we tend to seek and tolerate time alone in a nonlinear way throughout our mortal journey from childhood to older adulthood. How we spend that time seems to matter quite a bit in terms of our contentment in solitude, as do the nature of our relationships beyond solitude. Solitude is like a garden in different seasons, what we sow and what we reap changes over time, and we have to be certain to plant what’s most likely to grow and thrive.

How fast or slow does the process of dysregulating the stress response system go before a disease emerges? This chapter builds a model for how this process works over the lifespan. The apparently sudden onset of diabetes or heart disease in our fifties or sixties can often be traced to dysregulations that began years or decades before, invisible to the unsuspecting and asymptomatic. Toxic stress accelerates illness and speeds up aging. How do we know if we’re on a fast track to future illness and early death? And when is the best time to intervene? That depends on how we measure stress. Consider Teresa Langford’s pathways from genes to stress to illness over 53 years.

In this chapter, we review existing literature on the development of prosociality throughout the lifespan by highlighting the different factors/motives underlying individuals’ prosocial actions and their beneficial effects across time. First, we define the concept of prosociality and discuss the main theoretical issues related to its study from a lifespan perspective. Next, we review key empirical findings on prosociality by considering three main developmental phases (infancy and childhood, adolescence and young adulthood, adulthood and older adults) and we underline how an analysis of the main motives/factors operating in each phase can help explain the variability in prosocial development. Based on our review, we also offer some guidelines for the design of intervention actions that are developmentally appropriate and meaningful for the targeted age groups. Finally, we conclude by identifying potential gaps in the literature and we indicate promising directions for future studies.

Today the average lifespan in the US approaches 80 years old. However, the average health span—the number of healthy years we live—is much shorter. In the US it is 63 years old. This means we are living much longer than we are healthy. Disparity in health span is substantial in the US. The most privileged have a health span that approaches their lifespan. We must ensure that everyone has the opportunity to match their health span to their lifespan. Offering realistic guide posts on what to expect with normal aging. Crucial to put aging well at the center of policy internationally to harness the power of older people and move forward globally.

The introduction outlines the aims, methodology and time frame of the book, explains its structure and briefly introduces readers to the eight individuals whose diaries are the book’s principal source material. A succinct review of the literature on elite and popular ruralism in Britain follows, emphasizing that there has been far more research on the former than the latter. The pathbreaking work of Helen Walker, Harvey Taylor and Alun Howkins on popular ruralism is acknowledged and summarized. Although we now know much about the macro-history of popular ruralism (at least as expressed through the outdoor movement), we know much less about its micro-history – how the countryside fitted into the lived reality of people’s lives. This is the gap which this book aims to fill.

For many years, donor conception treatment was seen as a “solution” to involuntary childlessness, marked by pregnancy. Through awareness-raising by mental health professionals and especially donor-conceived people themselves, it is now increasingly recognized as the start of a family-building process with an ongoing story that unfolds over the family life-span and beyond. This chapter shows how parents’ abilities to adjust their prior beliefs about the meaning of “family” and “genetic relationships” become critical in the shift from “building a family” to “being a family” and onwards. Moreover, they are not alone anymore: various story-tellers in the new family system, including children, grandparents and others, each have their own unfolding understandings to voice and manage, separately and together. Throughout this creative and challenging process, the donor(s) has a presence, regardless of whether all are aware of their involvement. The complexity of disclosure is considered alongside the need for openness itself to be ongoing and interactive if it is to healthily accommodate shifts in understanding and power balances as children grow. Families do not exist in a vacuum, so wider networks and societal developments can also influence the permeability of their boundaries. Finally, the role of professional and peer support is considered.

The chapter explains the basic principles of linguistic change from a sociolinguistic variationist perspective. It begins with an explanation of the inextricable relationship between linguistic variation and change, and proceeds to demonstrate how language change can be observed, investigated, and explained. Sociolinguists can document and analyse language change using either the real-time method or the apparent-time construct; these methods and their advantages and pitfalls are explained and exemplified.