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.
Genes, Epigenesis, and Social DNA
The fundamental assumption of the current work is that modern humans (Homo sapiens sapiens) are the product of gene-culture co-evolution spanning at least the past 5 to 7 million years. Current knowledge about how the evolutionary process works has been advanced by three major milestones. The first was publication of Darwin’s The Origin of Species (1859) and The Descent of Man (1871). His revolutionary concepts moved questions about human origins from the realm of philosophy and myth to the discipline of science and established natural selection as the cornerstone of evolutionary biology.
The second milestone was development of the modern science of genetics. Genes were identified early in the twentieth century as the units of heritable traits, and seminal works, such as Dobzhansky’s Genetics and the Origin of Species (1937), laid the foundation for understanding gene flow through time and space. Discovery of DNA structure in 1953 revealed the molecular mechanics of how traits are transmitted. Later advancements in DNA sequencing in the 1970s and the 2003 reconstruction of the human genome are now allowing us to probe relationships among the ancient lineages of our family tree more deeply, often with surprising results.
The third source of enlightenment on evolutionary processes was the emergence of the field of sociobiology, officially launched in 1975 by E.O. Wilson’s Sociobiology: The New Synthesis, and its sequel, On Human Nature, in 1978. These works helped to establish an interdisciplinary approach to understanding the evolution of heritable physical and social traits in all animal species, including humans. The sociobiological movement overcame initial criticisms of biological reductionism and genetic determinism and went on to spur a wealth of new research that continues to flourish decades later.
The field of sociobiology hosted lively internal debates as well, not the least of which concerned the locus of natural selective processes. One school of thought places primary emphasis on the theory of kin selection. This concept, which originated in the earlier works of biologists Hamilton (1963, 1964), Trivers (1971, 1972), and Alexander (1974), proposes that individual organisms maximize their own reproductive success or “inclusive fitness” by behaving altruistically toward close kin, weighted by the degree of genetic relatedness. The theory, also known as “Hamilton’s Rule,” was supported by a mathematical formula that calculated that altruism will develop to the extent that the benefit to the recipient times the degree of kinship to the altruist is greater than its cost.
Kin selection as the principal driver of human social evolution gained widespread acceptance among biologists, including E.O. Wilson, for about four decades. Commencing in 2010, however, a series of coauthored papers by Wilson and others challenged the mathematical and biological validity of kin selection theory as an explanation for the evolution of advanced
