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This book revisits fundamental questions on the biocultural origins of human sociality. What set our ancestors on a separate evolutionary path from that of other apes? What was the nature of primeval kinship and mating? What roles have biology and ecology played in shaping human social groups through time?

Scholarly musings on such questions have populated library shelves for decades. Various theories have been proposed, debated, embraced, rejected, and periodically recycled. In recent years, the scope of inquiry on human origins has been enriched by pioneering research across multiple branches of science. The findings of such studies, however, have not always informed one another in a manner that encourages a re-examination of current evolutionary theory. In other words, establishment of an academic lingua franca that facilitates the creation of integrative models has been elusive.

A primary goal of the present work is to reach beyond traditional schools of thought and foster a cross-disciplinary dialogue on human social evolution. The task is to unravel the fabric of existing theories, explore new independent discoveries on the emergence of our genus, and tie together the myriad threads of this evidence in novel ways. This is arguably an arrogant undertaking, given the impressive lineup of experts who have already offered their insights on the subject. But experts currently disagree, both on the principal drivers of human evolution and on the nature of ancient social forms. Finding new answers to old questions often involves being a contrarian on some levels, and an adventurer on others. It also requires a measure of humility, since all accounts of human social origins are necessarily speculative.

Theories on the origin of society are neither new nor in short supply.¹ It is a subject that has fueled the imagination of both religious and secular philosophers for centuries. It has also spawned a robust body of scientific evidence, primarily in the fields of anthropology, paleontology, and evolutionary biology. Significant fossil and archaeological discoveries have provided the foundation for chronological reconstructions of our biological and cultural journey over the past 5 to 7 million years. Ancient material remains have shed light on the subsistence activities, technologies, settlement patterns, migrations, and cognitive abilities of archaic populations.

Insights into the evolution of human social behaviors, however, are constrained by the natural limitations of what bone and stone artifacts can tell us about the nonmaterial aspects of ancient sociality. How did our ancestors structure mating, labor, food sharing, kinship, and power relationships? To what extent did biology shape these behaviors? How did ecology influence the prevailing social architecture of human groups in both time and space? What role did primate brain evolution and the emergence of symbolic communication play in the trajectory of early social life?

Since we cannot travel back in time to the encampments of our forebears, answers to these questions have to rely on the construction of conceptual models. However, creation of models with clearly defined premises and measurable outcomes is particularly challenging when the task is to explain the origins of phenomena that are no longer directly observable. Interpretations of the fossil and archaeological records have therefore been traditionally combined with observations of contemporary nonhuman primate communities and of historic hunter-gatherers to paint a picture of what Paleolithic social life may have been like.

One of the earliest and most influential of these models was crafted over a half century ago. Commonly referred to as the “hunting hypothesis,” it proposes that the first apes to achieve a successful terrestrial existence on two legs established the social mold from which all subsequent forms of humanity were cast. The adaptation of our ancestors to a carnivorous life on the open savanna, it argues, served as a sort of primeval Petri dish for the germination of a distinct complex of traits—traits that predisposed early humans toward a uniform pattern of reproductive behavior, labor division, and kinship organization. Early sociobiological models argued further that this trait complex was so intimately connected to survival that it became genetically imprinted. In this view, the social life of Paleolithic peoples conformed to a standard template, one dictated by a biogram that not only was perfected by natural selection in ancient times, but continues to dominate the reproductive and social patterns of modern humans.

This monotypic model of human social evolution has enjoyed such popularity over the years that it is sometimes referred to as “the standard narrative.” The image of early humans organizing themselves into small male-centered family groups and wandering over parched landscapes in pursuit of sparse game is remarkable by its persistence, particularly in light of subsequent research. In recent decades, fossil, archaeological, and ethnographic records have expanded exponentially, along with our understanding of primate sociality. The hunting hypothesis and its implications for human social life have come under numerous challenges, but such debates have taken place largely within the confines of specific disciplines, such as anthropology and paleontology. Meanwhile, several ancillary branches of science, such as climatology, paleoecology, paleogenetics, and neurobiology, have been exploring their own avenues on the conditions affecting the evolution of our genus, many of which have significant implications for the nature of ancient social life. These new research findings are impacting traditional notions about what early humans ate, where they lived, how their brains evolved, and how ecology and the reproductive strategies of the sexes may have impacted the nature of social groups. In short, many of the fundamental assumptions of existing models are beginning to erode, but robust cross-disciplinary dialogue on these issues has lagged.

Rethinking human social origins is an exercise in collaborative inquiry. Such is the challenge of this book. Recalibrating current evolutionary paradigms is difficult, in part because it often requires a departure from academic comfort zones. Institutions of higher learning create disciplinary and subdisciplinary silos—each with their own legacies of specialized knowledge, jargons, and world views—that constrain the cross-fertilization of ideas. Experts don’t always talk to one another or, worse, become vested in their own viewpoints and stewardship of specific schools of thought. A major historical divide, for example, has existed between biological and social anthropologists with regard to the origin and nature of human kinship systems. If productive dialogue is sometimes constrained by banter and debate within individual disciplines, communication problems are compounded by the isolation created by institutional boundaries between them. The need to establish a more comprehensive dialogue on human social origins has recently been highlighted by Callan (2008) and others, such as Mills and Huber (2005), who have proposed the concept of intellectual “trading zones” to foster the communication of ideas across traditional academic disciplines.² In short, progress on theoretical questions such as the structure of ancient social life requires a lowering of technical and research boundaries and a more effective way to disseminate and integrate relevant data among scholars from widely disparate fields.

Progress on the refinement of conceptual models also requires a reassessment of cultural and individual biases. Scientific inquiry is an imperfect exercise. It assumes that the scholar approaches the examination of a problem dispassionately, developing insightful hypotheses and then objectively unraveling certain truths through a process of vigorous inquiry or testing. While some disciplines, such as mathematics, naturally lend themselves to the discovery of empirical proofs, others struggle to assemble fragmentary bits of information into some kind of formula or model that purports to explain extant conditions or end states. That assembly process often draws on an assortment of facts, hunches, and a priori biases, the segregation of which may be murky for both the scholar and the intended audience.

Ideally, authors of theoretical books such as this one should be required to devote their first chapter to a declaration of their underlying assumptions and predilections. This exercise would facilitate the author’s own awareness of the preconceived notions and agendas they bring to the table. It would also key the reader to factors that are likely to color the author’s focus of inquiry, selection of data, and conclusions drawn. An ancillary benefit of this early-warning system, of course, is that it would also provide an opportunity for the reader who disagrees with the book’s initial premises to return it to their retailer unread for a full refund. In most cases, however, it is a fair bet that readers would probably welcome a clear exposition of an author’s starting point and the opportunities for constructive debate that such honest dialogue provides. This introduction is written in this spirit.

The book thus begins with a summary of assumptions on eight general topics that have influenced this writer’s approach to the evolution of human sociality. This initial discussion draws attention to key issue areas in which recent cross-disciplinary research is both augmenting and redirecting our understanding of Paleolithic social life. Each will be discussed briefly, and an effort made to the elucidate how these baseline concepts are reflected in subsequent chapters.