of animal flesh—an accomplishment often credited with leapfrogging early hominins into the genus Homo.
Water, or the absence thereof, is seen by Boaz (1997) and Finlayson (2014) as a driver of increasing sophistication in early humans. Pleistocene climatic swings were accompanied by dramatic ecological changes, including the retreat of tropical forests, increasing aridity, and desertification. Such conditions are proposed to have selected for complex reasoning and strategies necessary for survival in the face of diminishing water supplies. Prevailing theories about life in the Pleistocene argue that early hominins, tethered as they were to sources of water, were forced to increase their mobility and geographical range, limit their group size, adopt new technologies, and/or embark on migrations to more favorable habitats for sustenance.
Such theories acknowledge the critical importance of water sources for quenching hominin thirst. But notably, they are generally silent about the extent to which rivers, lakes, marshes, and marine shorelines also contained the necessary food sources to fill their bellies. Such well-watered habitats, which support a wide variety of flora and lipid-rich fauna, were variably distributed throughout Africa and Eurasia even during the waxing and waning of glacial events. These premium habitats were theoretically capable of supporting sizeable populations on a seasonal or year-round basis. Not coincidentally, this is precisely where hominin fossils are most frequently found. This book will examine recent paleoecological research and archaeological evidence that underscores the importance of mosaic habitats and aquatic resources in early human adaptations.
The implications of well-watered habitats and resource diversity for early human social life are profound. Periods of extreme aridity did occur during the Pleistocene. Lakes and rivers in some regions did dry up. But surviving populations were necessarily opportunistic. It is equally probable that, as an alternative to settling for a Spartan existence on the arid savanna, enterprising hominins simply followed existing waterways and coastal highways to more favorable habitats, or shadowed the advance and retreat of glacial ice seeking the “ecological release” of untapped environments. This book will re-examine what we know and what we think we know about the hominin Plio-Pleistocene diet and how these assumptions color our vision of early human communities.
Ecology Drives Social Forms
Traditional theories on human social evolution often weave the mating and economic dimensions of reproductive success into a single fabric, one that assigns a primary role to male inclusive fitness. In this view, ancient genetic propensities that wed male sexual and economic dominance are proposed to define not only the dawn of human kinship and the division of labor, but much of what drives contemporary reproductive behaviors. The resultant social forms proposed as primal markers of humanity thus become monotypic or one-dimensional, with exceptions viewed as aberrant or unnatural. Such models create a single Paleolithic prototype that is largely impervious to ecological variation.
In contrast, the multilevel selection perspective advanced in this book provides a framework for understanding the factors that impact the inclusive fitness of both sexes and the variable structuring of social relationships based on common kinship. A basic assumption is that human sociality evolved as a vehicle for reproductive success. Selective factors operated to increase fitness by not only structuring mating behaviors and relationships among close kin, but by structuring relationships among community members in a manner that optimized their procurement and distribution of fitness-related resources, such as energy, materials, genes, and information. Hominins evolved epigenetic playbooks, or social DNA, the phenotypic expression of which calibrated social systems with the nature and availability of critical resources in a given niche. The architectural types of human social groups have been limited in time and space and have conformed to a finite set of rules. Mating relationships may be predominantly monogamous, polygynous, polyandrous, or polygynandrous.8 Similarly, social forms that define economic units and access to resources are of limited types. For most of prehistory, they have been based on the recognition of either uterine (related female) or agnatic (related male) kinship. While the number of social DNA variants (“epialleles”) is small, their phenotypic expression is plastic and importantly linked to ecological conditions.
Pleistocene habitats on the African and Eurasian continents were both dynamic and diverse. Some were arid, some well-watered. Some offered year-round abundance, others only seasonal or scant resources. All were subject to climatic events that choreographed the changing demographics of species. This book proposes that hominin populations occupied a wide range of niches throughout their evolutionary development. Social DNA or epigenetic mechanisms of inheritance provided evolving humans with the capacity to flex their social strategies in characteristic ways to meet the challenges presented by changing landscapes. The social forms that structured these adaptations, namely, multigenerational kinship units, are of limited types. Uterine and agnatic social organization have distinct demographic, social, and political consequences that correlate with ecological factors. Their phenotypic expression should therefore be predictable in general outline. The final chapter of this book explores the rise and fall of Paleolithic kinship groups and the ecological dynamics on which they may have been predicated.
False Prototypes
If Homo sapiens sapiens were the only primate to survive to modern times, the task of breathing life into ancient fossil remains would be doubly challenging. Our ability to observe the behaviors and social life of contemporary apes and monkeys provides an opportunity to identify traits that may be markers of our common ancestry, and hence perhaps equally shared with proto-human populations. Earliest attempts to utilize observations of primates in the wild as a window to societal origins were commonly based on savanna baboons, not only because they were the most highly studied, but because they were thought to occupy human primordial habitats. Lionel Tiger (1969), for example, envisioned baboon male dominance hierarchies as a genetically based precursor to male bonding requirements of the hunt, activities claimed as pivotal to human evolutionary development on the open savanna.
In the succeeding decades, additional studies have more clearly defined the complexity of baboon social organization, along with that of chimpanzees, bonobos, and a variety of Old and New World monkeys. Such studies have provided new information on primate sexuality, male and female dominance hierarchies, and social networks, along with an appreciation of how such behaviors respond to ecological factors. While patterns common to contemporary nonhuman primates provide valuable insights for reconstructing our ancient past, there are some cautionary notes.
Models based on a single species observed in a single habitat are subject to the whims of the author’s choice, and therefore may lead to false generalizations or conclusions. The same may be said about reliance on modern apes as avatars of our ancient past. It is important to remember that all contemporary nonhuman primates have been forced into marginal habitats that are not representative of Plio-Pleistocene ecological conditions. Some apes, such as gorillas and chimpanzees, have been refugees for millions of years, retreating and adapting to the isolation of shrinking African tropical forests. These and other primate species have also suffered repeated encroachments by Homo sapiens, conditions that may enhance competition for resources and fundamentally alter their behaviors and the structure of their communities.
The same cautionary note applies to models of Paleolithic society, which have historically been based on contemporary hunter-gatherers. Virtually every anthropology text on human cultural evolution portrays the !Kung Bushmen, Hadza, or Australian aborigines as examples of what preagricultural life was like in the Pleistocene. The predominant theory has been that the earliest humans emerged with a dietary reliance on animal flesh and ranged into the open, semi-arid savanna as small, highly mobile hunting bands. The so-called hunting hypothesis grew out of conferences and symposia in the 1960s and its standard-bearer, the patrilocal band, was long memorialized in the anthropological literature as the earliest stage in human cultural evolution.9
One of the cautions of viewing lifeways of contemporary hunter-gatherers
