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Whole books, and sections of books, have been dedicated to reviewing the intellectual history of multilevel selection, some small swath of which are considered in this first chapter. Readers are then made aware of other pertinent publications, acquiring something of their substance in this condensed review. For example, readers will certainly gain knowledge of multilevel selection’s prototypical origins as they are present in Darwin’s Descent of Man, while also being introduced to its reformulation a century later as a measure of population regulation. In addition to preferring main ideas to tortuous detail, we here take such content’s subsequent relevance as our litmus test for inclusion. We also review recent bouts of controversy between adherents and detractors. Where historical review is the end of other books, we use the history of multilevel selection instrumentally, with the end of contrasting its original formulation with its present instantiation. Having drawn these distinctions, one can clearly see that most controversies and objections no longer apply, as they do not pertain to modern manifestations of multilevel selection. Even as naysayers continue to criticize it for something it either never was or no longer is, the modern formulation of multilevel selection is becoming known to, and accepted among, most evolutionists. Nevertheless, this is only the first act in the two-part drama, taking us to the lowest ebb of multilevel selection’s reputation. The astute reader may notice that we use the expression multilevel selection when referring to the more general theoretical framework that is the subject matter of the present volume, while reserving the term group selection for describing the positions of past commentators that directed their reflections specifically to this particular component of multilevel selection theory, especially as more narrowly defined by past formulations of this principle. Multilevel selection theory is a more inclusive term that recognizes the operation of selection at multiple levels of biological organization, including both solitary individuals and social groups, as exemplified but never explicitly named by Charles Darwin’s thinking on the matter.

The previous chapter depicted a rising chorus of consensus starting in the 1970s. Sober and Wilson describe how group selection was buried in the 1960s and 1970s and treated with utter contempt. It was so reviled that it was not forgotten, but recalled as an example of how not to think. Even in the 1980s, as Sober and Wilson recount, an unidentified, distinguished biologist once advised a younger colleague that there are three things that one does not defend in biology: group selection, phlogiston theory, and Lamarckian evolution. Indeed, discussion of group selection, at certain points in the history of evolutionary biology, evoked criticism and even ostracism, as illustrated by the following reflection shared by the still skeptical professor Detlef Fetchenhauer (2009)

As exemplified by the history of the Roman State, economic distress can decrease the level of intrasocietal cohesion even in the absence of external pressures. Since its inception, the Roman Republic faced numerous foreign threats, from rival cites in the Italian peninsula to tribal confederacies in Gaul. A chronic state of intergroup conflict favored the evolution of cultural variants necessary for sustaining large-scale cooperation. These innovations allowed the Republic to conquer its neighbors and expand outside the Italian peninsula. Even though the spoils of war created a climate of macroeconomic prosperity in Rome, the rising income and wealth inequality, along with the elimination of ultrasocial institutions, increased popular discontent. It was during these times of turmoil that ambitious men dismantled the foundations designed to guard the State from the exploitation of autocrats. Debates concerning land and wealth distribution, at first restricted to senatorial rhetoric, escalated into street revolts and political assassinations. The mobilization of “private armies,” as part of a series of civil wars, would eventually lead to the end of the Republic.

This chapter is the first of five comprising Part III. Though, as in Chap. 6, we have previously allowed some lexical analyses to interpolate Part II’s historical-empirical thrust, Part III is predominately statistical, even as it continues to review relevant literature and history. Though, consistent with the mandate of this monograph, we aim ultimately to establish the reality of human group selection, this initial chapter alone treats chimpanzees. To thoroughgoing evolutionists, the relevance will be self-evident; we only add that establishing evidence of group selection in such a highly related species foundationally supports the empirical argument for human group selection, as presented in the four subsequent chapters constituting Part III of this volume.

This chapter will provide a synthesis of the current evolutionary literature concerning lethal coalitional aggression in small-scale societies. Attacks, raids, skirmishes, ambushes, and other forms of intergroup aggression present significant risk of injury or death, irrespective of group size, though the means of differentiation among groups, like the mechanisms of ensuring coordination within groups, change as a function of group size. Human coalitional violence is often explained via kin selection and reciprocal altruism, such that an individual’s assumption of risk is compensated by fitness-enhancing benefits to relatives and allies. These explanations become increasingly inapplicable in progressing from bands and tribes to chiefdoms and states. The growth of larger social aggregations compelled the emergence of institutions enforcing intragroup cooperation above and beyond the effects of underlying social networks based on kinship and direct reciprocity. Perspectives reviewed herein, such as cultural group selection, consider the cultural evolution of such institutions in generating between-group variance and facilitating lethal intergroup competition. According to these theories, cultural transmission, group differentiation, symbolic ornamentation, punishment of defectors, and ethnocentrism are integral components of intergroup competition, with lethal coalitional aggression being an extreme manifestation of between-group rivalry. Furthermore, due to the significant fitness costs imposed upon defeated factions, the study of lethal coalitional aggression in small-scale societies provides fertile ground for examining the interaction between group-level and individual-level selective pressures.

The subject of societal collapse is a theme that, due to its political, social, economic, and ecological implications, still generates heated discussions. Researchers interested in developing a general theory of collapse face the challenge of identifying common patterns across human societies. This task is further complicated because multiple publications on the subject employ a case-by-case methodology, within which the causes of collapse are thought to be specific to each society. Such historical particularism persists to this day. Historical contingency is preferred to generalizable explanation. In response, some researchers have instead concentrated on examining how a society’s internal dynamics predict the risk of collapse. For example, a society’s institutional performance, macroeconomic yields, and level of collective action have been thought predictive of its structural integrity under adverse circumstances. Through this lens, external factors may lead to a sudden loss of sociopolitical complexity only when the system’s capacity to address these conditions is compromised. Given variation in societies’ level of cohesion and collective action, the case of societal collapse offers a unique glimpse into multilevel selection operating among social systems. This chapter describes critical elements developed in the collapse literature while providing an overview of the current multilevel selection perspectives on fluctuations in collective action. The present chapter also describes how institutional robustness and cultural innovations contribute to a society’s regeneration capacity after experiencing a collapse.

The content of the previous two chapters described mathematical models and presented relevant empirical data pertaining to multilevel selection as a proposed biological universal within the general framework of evolutionary theory. The present chapter turns to phenomena that are believed to apply more specifically to humans. Consistent with the Darwinian principle of continuity, we are not claiming that humans stand alone as somehow separate from the rest of animal nature, given that the differences between human and nonhuman animals are most often differences in degree and not in kind. Nevertheless, there is also a case to be made that all species are to some extent unique and distinguishable from each other based on species-typical characteristics. Following from the principle of continuity, humans are not excepted from the forces of multilevel selection. Nevertheless, humans are unique by virtue of our species-typical characteristics, and so have a unique relationship to multilevel selection deriving from our unique evolutionary history. If we infer correctly, Wilson (2015) concurs with this assessment, figuring among those few authors who recognize the human species as having been particularly susceptible to multilevel selection throughout our evolutionary history. As an explanatory framework, multilevel selection might therefore be most interesting, elaborate, and probable among human populations precisely for the many complex qualities that qualify as human. This section, and all the sections that follow within this chapter, can then be understood to explore the unique properties of humans, both as they were shaped by multilevel selection and as they allowed multilevel selection to assume unprecedented effects and directions. In sum, when simultaneously considering the aforementioned principle of continuity alongside species-typical human universals, one finds certain principles of multilevel selection uniquely applicable to our species and not many others. To fulfill this mandate, we provide prerequisite knowledge of cultural evolution theories, gene-culture coevolution, and cultural group selection before closing with an integrated section embedding group selection within the larger framework of multilevel selection theory.

This chapter and the three that follow collectively comprise Part II of our book, respectively, entitled “Aggregation, Growth, Decline, and Collapse.” Thus, these four chapters collectively comprise a theme familiar to declinists and students of cyclical history. As will be reiterated in later chapters, each of these processes must be studied in abstract after the manner of traditional scholarship, as has been pursued by Gibbon, Vico, Toynbee, Ibn Khaldun, and Spengler. However, it will also be important to update some of the theories proposed by these past historians with subsequent discoveries. Furthermore, as this is a book on multilevel selection, we separately and systematically consider the influence of group-selective pressures as they contribute to aggregation and state formation, the decline of mature civilizations, and their eventual collapse.

Where Chap. 4 reviewed the formation of sociopolitically complex civilizations, this chapter reviews their growth and maintenance. Mature states invariably come to encompass expanding territories and consequently absorb populations distinct in dialect and language, ethnicity and race, and culture and religion. As discussed herein, maintaining integrity at a particular level of group size comes from managing both sources of threat: managing one’s own population while defending against rival groups. Populations must be bound by some combination of custom, sanctions, religion, and legal infrastructure. To the extent that this can be accomplished, a state must radiate control stably through time, as indicated by the Roman Empire and contraindicated by the conquests of Alexander the Great. Controls necessary for stable growth can be (1) psychological, as with propaganda; (2) legal, as with incarceration; (3) social, as with banishment; (4) martial, as with conscription; or (5) economic, as with taxation. Some controls woo and win elites, ensuring allegiance through shared interest, title, rank, privilege, estates, orders, and garters. With reliable money as a medium of exchange, states ensnare citizens within a tightening cage of mutual interest, trade, dependencies wrought of divided labor, and the attractive ability to solve collective action problems. All such forms of control foster growth and allow for societal maintenance.

In 2017, our research team produced a technical, statistically driven, monograph entitled The Rhythm of the West: A Biohistory of the Modern Era, AD 1600 to the Present. Therein, general intelligence, life history, and other topics were treated alongside multilevel selection theory. Here, after providing a general overview for the sake of context, we extract findings and discussion points from The Rhythm of the West directly relevant to demonstrating the reality of group selection within the history of the Britannic peoples. In a colloquial and qualitative manner, displaying essential analyses and separated from ancillary topics, we explain group selection among the Britannic peoples as they have transitioned through stages of expansion, fission, and decline. Wealth, cognitive capacity, subjective well-being, poverty, and longevity are among the oblique markers of civilizational pulse. These correlate with, and are corroborated by, demographic decline. Declining evolutionary pressures for group-selected behaviors within mild industrial and postindustrial environments, operating for generations, have had a causal role in population decline, both in absolute and relative terms. To describe and explain the aforementioned decline, we review a variety of changes to Europe’s Early Modern Era selective regime, including climatic changes during the Little Ice Age, niche expansion and modification during the Age of Exploration, nutritional advances gained during the British Agricultural Revolution, and technological advances gained during the Industrial Revolution.

Introductory psychology classes and texts invariably feature attachment theory, which is rightly regarded as a pillar of the field. The acknowledged founder of attachment theory, John Bowlby, resisted the tide of psychoanalysis and instead pursued a more biological explanation of parent–child relations, characterized by insecure attachment variants as dysfunctional miscarriages of mother–infant bonding. Contrary to Bowlby’s assumptions, the supposed pathology of the insecure attachment is reframed by life history evolution as strategic adaptation to reproductive ecologies. While insecure attachment is not specifically adaptive, eliciting rearing behaviors displayed by parents, like early sexual debut, mate diversity, completed fertility, and other resultant mating behaviors displayed by the child at maturity, are adaptive within unpredictable and stochastic environments.

In his Atlas of World Cultures, George Murdock catalogues more than 1000 discreet populations of peoples that are too often amalgamated at the level of the nation-state. For each of these ethnically informed cultural populations, Murdock provides nearly fifty points of tabular ethnographic codes, including mating systems, kinship networks, levels of consanguinity, post-marriage living arrangements, type and intensity of agriculture, settlement patterns, and social fluidity, which are then combined with environmental statistics such as latitude, and primary and secondary climate classifications. This chapter asks and answers questions concerning Galton’s Problem, finding commonalities among contiguous cultures to extend, not simply from contiguity, but from shared selective pressures. Murdock’s cross-cultural classificatory variants therefore derive from ecologically driven evolution, as described in social biogeographical applications of life history theory.

Like Toynbee, William McNeill is a world historian, but one with a bent toward epidemiology. Most directly in his Plagues and Peoples, McNeill considers the role of disease-induced mortality, infection, and transmission alongside the more traditional historical topics of war and conquest. McNeill studied disease as a primary cause in its own right, rather than as incidental sequelae to climatological catastrophes, famine, war, or resource limitation. McNeill anticipates the emphasis placed by modern evolutionary life history theory upon regimes of extrinsic mortality as being the main drivers shaping life history evolution. After all, from its founding, life history has incorporated population density and mortality rates into its quantitative formulae and qualitative theory, making it an ideal framework from which to reconsider McNeill.

Written over decades, subsuming much of his career as a sociologist, Michael Mann’s four-volume Origins of Social Power pursues one grand theme: Societal aggregation from tribe, to fief, to city-state, to nation, to empire. Mann uses the term, “patterned mess,” in recognition of cultural, historical, and temporal particularities which overlay sociological laws as they have operated through time. Modern theories of gene–culture coevolution work precisely in this way, in that they operate on a fundamental level, even as surface features vary. So when Mann studies internal divisions and external competition as they ebb and flow creating regression and progression along this continuum of aggregation, it is now possible to partially explain this as a function of variation across aggregate life history continua.

Bound together by virtue of their shared mission to explain human nature and society, the social sciences have unity of purpose even as they have no meta-theory; there exists no foundation from which variables can be connected, causally sequenced, or ultimately explained. By way of an overview in abstract, this first chapter introduces life history theory, the meta-theoretical pretentions of which are demonstrated during the remainder of the book by reading geographers, demographers, historians, anthropologists, sociologists, and psychologists in life history evolutionary perspective. Thereafter, comes a survey of the anatomical structure common to the eighteen core chapters, which are divided into four parts, beginning with an overview and concluding with a theoretical proof. These core chapters are grouped into six sections, each ending with a meta-commentary.

With eminently unpropitious timing, Thomas Robert Malthus wrote of resource competition just as humans were bursting the bonds of organic economies. An Essay on the Principle of Population, in warning of the ills consequent to population density and resultant resource competition, may have, however, underappreciated its evolutionary effects. Although the significance of mortality regime has superseded its overall significance, population density, and the resource competition it brings, was the variable around which life history theory was originally constructed. With the coming of density and accompanying competition, life history theory explains how populations change and stratify as they vie to survive and reproduce. As herein argued, the slowing of life history is a consequence of population density that Malthus could not suspect, but might have appreciated.

Montesquieu incorporates what would now be understood as political science and ecology into his eighteenth-century sociological studies. He concluded that sociopolitical systems were outgrowths of ecological conditions, and so cannot be unthinkingly transplanted from locale to locale. Already extant, there are evolutionarily informed studies of Montesquieu’s thesis using variables such as group-mean intelligence, which validates the relation between ecology and the development of monarchies, republics, and despotisms. However, this fourteenth chapter shows that this is but a part of a larger process. Human populations respond to ecological conditions through changes in mean intelligence, but also through changes in other life history traits. Consequently, it is inter-population life history means that were obliquely observed by Montesquieu to give rise to sociopolitical differences.

Through his Bioecological Systems Theory, Urie Bronfenbrenner emphasized school, parish, neighborhood, and other aspects of what behavioral geneticists now call the extra-familial environment. Bronfenbrenner incorporated even the economy, government, and culture into his developmental scheme, knowing that these macrostructural realities trickle-down to influence more local systems, if not the child directly. As recounted in this chapter, life history theorists have extended ecological systems theory such that it incorporates natural ecological systems, not limited to temperature, humidity, parasite prevalence, resource availability, and population density. An evolutionary view of Bronfenbrenner’s Ecological Systems Theory then clarifies the extent and direction of influences, while also adding a basement layer of natural ecology that constrains all other levels of influence.

In the late Victorian era, one could find Ellsworth Huntington caravanning through Eurasia, counting tree rings in northern California, or subsisting on stipends on the fringes of Yale’s geology department. Writing on demography as much as geography, Huntington described non-random change through founding effects and migration, as much as natural and sexual selection. Importantly, he distinguished between physical and community ecology, applying these concepts to human biogeography. Though not available to Huntington who wrote most prolifically in the earliest part of the twentieth century, life history evolution is indispensable to understanding the dynamics of climatically induced evolution across populations treated, for instance, in The Principles of Human Geography and The Human Habitat. Through Huntington’s writings, cross-continental variation in life histories is introduced and explained.

Raymond Cattell distinguished crystallized intelligence, akin to stored knowledge, from fluid intelligence, akin to raw reasoning abilities. Likewise, he delineated personality into component parts. Though intelligence and personality each qualify as subdisciplines within psychology, both are subsumed, along with other traits, under the meta-theory of life history evolution. The relationship is profound, though not straightforward. As described in this chapter, both intelligence and personality vary along a life history continuum, such that, as life history slows, population mean intelligence increases, as do personality traits like risk aversion, conscientiousness, anxiety, and agreeableness. Nevertheless, this effect occurs on average, and there is strategic variation occurring, which obscures the relationship between population-mean intelligence, personality, and life history. Once understood, these relationships color and clarify Cattell’s life’s work.

James Casey researches regional variation in lineal descent, consanguinity, and patterns of inheritance as they alternately impede or impel state formation. Joined by a spirit of capitalism, a market economy, and the division of labor, lineal descent, consanguinity and patterns of inheritance each had a role to play as drivers of state formation, and markers of progress toward social complexity. To the degree that kinship bands persisted, they acted simultaneously as an impediment to autonomous household formation, and to formal state formation. As Casey contends, changes in family organization underlay changes in social organization. Building upon this insight, as this tenth chapter describes, precipitating ecological drivers and concomitant evolutionary consequences cannot be absented when explaining the historical transition from consanguineous tribe to genetically diversified state.

Alan Baker’s work documents the fulfillment of the Neolithic Revolution with its mature societies resting on a foundation of staple grain crops. In Studies of Field Systems in the British Isles, Baker studies agriculture and its laboring class, while in Man Made the Land, he takes up the social outgrowths of agriculture. As evident in Baker’s studies of the French and English peasantry, much of the social changes following from agriculture are corollaries of population density. We interpret the technological advances, cooperation, and civilization as described by Baker, as outward manifestations of slowing life histories evolving through to historical time. Thus, Baker is eminently correct to assert that geography has shaped human history, even as he may not have been thinking of evolutionary history.

Where Edward Gibbon studied the Decline and Fall of Rome, Arnold Toynbee more generally studied the decline and fall of civilizations. The civilizational challenge is followed by a creative and adaptive response, or otherwise conquest and collapse. Across all studied civilizations, Toynbee returns to the theme of internal cohesion and its relation to external competition. In doing so, Toynbee touched upon some universal truths that underlie the cyclical view of history, though he emphasized the spiritual and circumstantial to the detriment of the geographical and biological. Nevertheless, Toynbee’s insights can be productively reinterpreted with life history evolution, such that his valid universal insights are qualified by particular inter-population variation, which ultimately chains cultural decline to its biological substrates.

Marvin Harris has taken the vagaries of culture and grounded them in ecology. From burning witches, to worshiping animals, to proscribing foods, Harris finds religious and cultural idiosyncrasies to proceed from ecological vagaries. More than this, Harris broaches social structure, demographic constraint, race, death, sex, and fertility, all of which are traced back to some knowable ecological determinant from which they probabilistically derive. Yet, like Keeley, Harris pointedly rejects sociobiological explanations. He believed evolutionary explanations of cultural differences to be impossible, insufficient, and unnecessary. As herein explained, these assumptions stem from a misunderstanding of how rapidly populations can evolve, unfamiliarity with life history theory and related sociobiological explanations that explain intraspecific diversity, and overconfidence in phenotypic plasticity and environmental explanation more generally.

Two centuries ago, Richard Price assisted in compiling the Northampton Tables, allowing lives to be insured with probabilistic rationality. This was part of a life’s work concerning the measurement of mortality risk. Though such early demographic investigations gained predictive power, explanatory power lagged behind. Herein we reread Price’s work on mortality risk using life history evolution, which, after all, is organized around mortality and longevity, making it an invaluable aid in understanding the actuarial life table. As can only be explained at length, it is apparent that Price, in measuring mortality, was indirectly measuring life history; and in applying his researches to life insurance, was in effect facilitating post-mortem parental care.

Lawrence Keeley was at the forefront of scientifically deciding between Rousseau, who saw civilization as corrupting noble savages and peaceable peoples, and Hobbes, who saw a war of all against all waged between peoples, clans, and tribes except if dominated by a Leviathan capable of monopolizing power and violence. Keeley came down firmly on the side of Hobbes, demonstrating the rampant violence and persistent warfare of pre-state societies. In the absence of life history theory, Keeley, and anyone else studying declining violence through modernity, is reduced to positing a host of explanations piecemeal, and thereafter finding it difficult to explain the positive feedback effect wherein decreasing violence, begets decreasing violence. Keeley explicitly abjures biological explanations of violence; a point directly addressed as this twelfth chapter evolutionarily interprets his findings.

John Landers is a demographer of pre-industrial Europe, acutely aware of bioenergetic resources as they are spent and accrued in a careful calculus. As if on a balance sheet, output must match input. Within such an empirically informed historical framework, Landers provides one of the most detailed demographic studies of eighteenth-century London, combining mortality data with fertility, population structure, and migration. As does the life history researcher, Landers pursues a more complete bioenergetic balance sheet than does Price or Malthus, reflecting demography as a discipline plotting ever closer to studying these many variables as a yoked complex. Extending from Landers, this seventh chapter describes an emerging application of life history evolution known as social biogeography, with its cascade of consequences proliferating across five ecological levels.

Distilled to its utmost, John Goldthorpe’s research depicts class as a coherent bundle of variables whose dynamic stability is only modestly responsive to social policy and temporarily disrupted by societal transitions. For all his descriptive prowess, Goldthorpe less successfully explains the origin and perpetuation of social stratification, and concomitantly, intractable limitations on social mobility. Especially as expansively described by Goldthorpe, class is a multifactorial construct partially tracking within-population life history speed variation. With that insight gained, the biological ballast of class stratification and stability can be understood as deriving from life history speed, which has genetic contributions that vary within populations. Thus, there is a biological ballast to social class, maintaining stratification even in the face of progressive social policies.