The essential message of this book is that Western populations are in decline, by which we mean that they are changing in a number of significant ways that are reasonably considered to be undesirable. Although this deterioration is manifest most clearly at the sociocultural level, we argue that its ultimate basis is in human biological evolution. Modern Western people have been losing a number of important traits, including intelligence and what might be called “existential vigor,” understood as an individual’s robust psychological commitment to his culture-bound way of life. This is apparent across a host of indicators of mental and physical health, intellectual productivity and ability, social cohesion, and perceived meaning in life. As they seem to comprise the foundation of advanced civilizations, the loss of these traits may prove catastrophic in the long run. The deepening of social isolation (declines in family formation alongside high rates of family dissolution; solitary living; preference for short- over long-term relationships), profane and narcissistic culture (secularization and rejection of all forms of transcendence, especially those encouraging sacrifice for anything other than individual hedonistic gain¹), and ideological/sub-cultural fragmentation (political strife; opposition to widely shared standards of behavior) all indicate societal degradation. None of these problems is likely to be corrected in the foreseeable future. They are all sequelae of an anti-civilizational evolutionary path on which industrialization and postindustrialization (collectively, “modernization”) have set all Western societies. We contend that the highest form of civilization is a complex, adaptive response to harsh and rare ecological and environmental challenges. When non- and anti-civilizational traits and corresponding behaviors are biologically permitted, that is, not selected against or even selected for, civilization is, in an important sense, no longer adaptive, and thus its basis starts to erode. It is cruelly ironic that since industrialization, civilized life has undermined itself by altering selection pressures such that they promote this outcome.

The current work aims to provide an evolutionary-behavioral theory of social development, which is intended to explain the historical ascendance of Western civilization, as well as, and more importantly, its recent decline and evidently grim future prospects. A key component of this latter part of our analysis is an explication of the distinctive psycho-existential idiosyncrasies of modernized Western peoples, particularly nihilism, the sense that life—whether it is one’s own or that of all humans or even of all animal organisms—has no point, and various mental health problems, especially depression, anxiety, and schizophrenia. This book is primarily a work of social science, which may seem strange given the breadth of topics that it covers and especially its biological emphasis. But we understand the relevant topics as broadly as possible, such that a wide set of variables pertaining to the condition of groups, societies, and civilizations requires our attention. One cannot devise an adequate theory of the current state of, or historical changes in, for example, the mental health of a population without considering biological and macro-sociological factors. Further, scientists are only just beginning to understand the dynamical interplay of these factors, including the “social” quality of the genome itself and its ramifications for broad trends in mental health. Nonetheless, our theoretical approach competes with a regnant paradigm that seeks to explain all group-level human behavioral variation purely in terms of “environmental” phenomena; this “environmentalist” alternative is often accompanied by an explicit or implicit hostility toward any explanation of human behavioral² (as well as social, cultural, etc.) variation that invokes biology. The theoretical and empirical poverty, indeed hopelessness, of this paradigm has been made overwhelmingly clear through research in the fields of psychometrics, sociobiology, human behavioral ecology, behavior genetics (including molecular genetic research), evolutionary psychology, and related disciplines. Alas, such work is little known in the behavioral sciences as a whole, and so we devote a chapter (Chap. 2) to apprising readers of relevant findings in these fields and critiquing the paradigm that would have us ignore them.

Our evolutionary-behavioral theory of social development builds upon and unifies a substantial body of research on the historical, biological, and psychological dynamics of Western civilization, in which two of the current authors have participated. Woodley and Figueredo (2013) and Woodley of Menie, Figueredo, Sarraf, Hertler, Fernandes, and Peñaherrera-Aguirre (2017) have provided substantial evidence indicating that Britannic populations reached their peak of general cognitive ability and intellectual productivity around the middle of the nineteenth century, roughly contemporaneous with the end of the British industrial revolution. A precipitous and ongoing decline in both of these domains followed. One successful hypothesis, propounded by Woodley and Figueredo (2013) and recapitulated by Woodley of Menie, Figueredo, et al. (2017), and tested by the latter, maintains that the harsh and variable environments and ecologies of Early Modern Europe—due primarily to low but fluctuating temperatures and resultantly brutal winters that constituted a “Little Ice Age” in this period—shifted the balance of selection pressures on Western populations strongly to the group level, placing them primarily under group selection,³ and that both these group-level and the remaining individual-level selective pressures favored high levels of general intelligence in these populations. Selection shifted in this way because resource scarcity in this difficult environmental and ecological context provided a fitness advantage to those populations that acted as groups to enhance their share of resources via inter-group conflict (war). General intelligence was selectively favored insofar as it increased the ability of individuals and groups to meet the many novel challenges that they faced in these trying conditions. Additionally, Woodley of Menie, Figueredo, et al. (2017) found that use of altruistic words sampled from Charles Darwin’s 1871 The Descent of Man reached a peak among Britannics in this group-selected phase, suggesting that group selection promoted altruistic dispositions that facilitated social cohesion and allowed Western populations to act as coordinated wholes in war. Other studies suggest that these same selective patterns applied historically to the Japanese (see Fernandes, Zerbe, Peñaherrera-Aguirre, & Figueredo, 2021). As modernization took root and advanced, the use of altruistic words fell along with intellectual achievement and general intelligence. The decline appears to have continued.

With a similar eye to evolutionary changes among Western populations over time, Woodley of Menie, Sarraf, Pestow, and Fernandes (2017) advanced a new theory, the social epistasis amplification model (SEAM), to account for apparent fitness-depressing behaviors and traits in Western populations following industrialization—for example, sub-replacement fertility and the apparent rising prevalences of personality and other mental disorders. This model posits that relaxation of negative selection, that is, selection against deleterious mutations, in Western populations via profound reductions of sources of morbidity and mortality (mainly through industrialization and subsequent macro-sociological processes) has had and continues to have adverse effects beyond genetic damage accruing to carriers of deleterious mutations. Evidence was presented that via social epistasis, that is, interorganismal genomic transactions, the effects of harmful mutations can be amplified to non-carrier humans and the broader group behavioral ecology, especially if those affected by deleterious mutations have high social status and thus roles in creating, shaping, and maintaining norms of behavior.

Here we argue that patterns of social epistasis and selection regimes are interactive, with civilizational behavior depending crucially on a fragile configuration of the two. A critical premise in connecting these phenomena is that the costs of defeat in war are severe: losing populations face potentially substantial reductions of fitness.⁴ It is thus essential that those populations under group selection and competing with other groups via warfare be attuned to and able to thwart all major threats to the integrity of their groups, both without and within. Based on the work of Woodley of Menie, Sarraf, et al. (2017), we term social epistasis that issues from deleterious mutations, and that has in all likelihood universally negative effects on group and individual fitness, negative social epistasis , and argue that it has the potential to substantially undermine the fitness of groups it afflicts. It is known that those Western populations that were likely under group selection exercised rigorous cultural controls, and thus had l...