Social DNA. M. Kay Martin

contemporary apes, such as behavioral plasticity, dietary breadth and food sharing, social demography, and cognitive function. Social DNA entertains the notion that traditional academic emphases on phylogenetic chronologies, material culture, and gross brain or neocortex size has led to an underestimation of ancient hominin ingenuity, intelligence, and social complexity. A central theme of this discussion is that early hominins were, in some ways, like every other primate, but like no other primate. That is, while primates respond in similar ways to similar environmental cues, there are important threshold differences. Contemporary nonhuman species have evolved as specialists, bound by genetic platforms geared to specific niches, whereas hominins evolved as generalists who came equipped with a more diversified gene-culture playbook that broadened their ecological range.

      The final section of this book returns to seminal questions about the essence of human kinship. It challenges current theories that tie kinship systems to innate dominance patterns, evolutionary stages, monotypic biograms, or phylogenetic continuity with chimpanzee-like apes. Instead, it proposes that the nature of human kinship systems is not preordained, but rather is the phenotypic expression of epigenetic rules (“social DNA”) that optimize the procurement and allocation of fitness-related resources in a given niche. Characteristic patterns of social group formation based on kinship alliance reflect rules for the regulation and distribution of resources critical to survival, such as energy, materials, genes, and information, that are adaptive in specific ecological settings. Matrilineal and patrilineal kinship systems are understood as variable social technologies for niche construction, with distinct architectures for structuring reproduction, labor, and political groups in relation to available resources.

      Social DNA is distinguished from other titles on human evolution in its scope of inquiry. New cross-disciplinary research findings are brought to bear on fundamental questions about the nature of Pliocene ecology, Pleistocene subsistence activities, hominin brain evolution, hominin life history changes, and the relationship of inclusive fitness to primeval kinship systems. It is my hope that this book provides a fresh perspective on our biosocial origins and responds to current calls for the creation of an enhanced dialogue across academic and disciplinary boundaries.

      I would like to extend special thanks to archaeologist Jon Erlandson, who graciously read and offered comments on parts of this manuscript. The ideas in this book are my own, but have benefitted from his insights on Pleistocene adaptations and the potential role played by aquatic resources in early human societies. Thanks are also due to my anonymous reviewers, who pointed out errors and omissions in the draft manuscript, and whose constructive comments resulted in improvements to this book. I’d also like to acknowledge ethnologist Isabelle Clark-Deces, who provided encouragement at the onset of this effort, and who left us all too soon.

      I am grateful to paleoartists Mauricio Anton and Emiliano Troco for agreeing to share their wonderful portraits of early hominins to illustrate this book, and to artist and friend Drew Fagan for his creative genius, technical support, and good humor throughout this project.

      Finally, I would like to thank my editors at Berghahn Books, Harry Eagles and Elizabeth Martinez, for their responsiveness and support during the book’s review and production.

Introduction

      SOME GIVENS

      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