to our Paleolithic past is that they are cultures in crisis. Khoisan-speaking groups such as the Bushmen were once dominant in eastern and southern Africa, but have been sequentially displaced from favorable ecological niches for centuries by Nilotic herdsmen, Bantu-speaking horticulturalists, colonial Europeans, and contemporary Africans. Similarly, various aboriginal ethnic groups in Australia were not only displaced from resource-rich coastal areas by Europeans, but decimated by genocide and disease. In both cases, depopulation and forced retreat into increasingly marginal habitats has systematically dismantled indigenous social and economic structures. While such societies can serve as useful models for how humans survive conditions of population loss and resource scarcity, the niches they currently occupy and to which they have been forced to adapt cannot be assumed to have dominated the Pleistocene landscape. These populations, like many nonhuman primate groups, are also refugees. The ethnographic present does not represent the ethnographic past.
A related critique of such prototypes is that the diversity of both contemporary and ancient hunter-gatherer adaptations has been systematically ignored (Martin 1974). Why, might one ask, when searching for historic or prehistoric hunter-gatherer examples that may potentially shed light on how Pleistocene populations lived, are the inhabitants of more resource-rich environments not considered? While climate change and increasing aridity were certainly factors affecting the evolution of our species, the impacts of these changes were unevenly distributed in time and space. Some areas of Africa and Eurasia may indeed have experienced rhythms of aridity that mimicked the challenges of today’s Kalahari and Australian deserts. But there were also vast areas of the Old World that remained well-watered and optimal for occupation by humans and other animals. Opportunistic members of all species followed the geography of these rhythms to their advantage. Those that did not perished. It is interesting to contemplate that if our ancestors were among those who chose to tough it out on the arid plain, our lineage may have ended up as just another in a long line of extinctions. The present book will entertain the notion that the ecological niches early hominins occupied and the adaptive strategies they employed through time were not uniform, but diverse. The Ice Age was a challenge that selected for ingenuity and plasticity, and is what made us who we are.
Aggress or Coalesce?
Behind every theory on hominin social origins is an underlying set of biases on what constitutes basic human nature.10 What are the innate propensities that govern intra- and intersexual behaviors, reproductive strategies, social structure, and intergroup relations? As noted earlier, some inclusive fitness models see society as a collection of individuals who engage in cooperative and competitive actions solely in pursuit of their own ends. This portrait of human reproductive behavior congers images of situational loyalties, dominance, subordination, parasitism, deceit, and betrayal. Other origins theories attribute the darker side of human nature to adaptations thought to have accompanied the shift of early hominins from arboreal to terrestrial life. For example, some argue that hunting on the open savanna turned our ancestors into bloodthirsty killer-apes, fierce defenders of territories, and combatants in endemic warfare over mates and scarce resources. A penchant for aggression and violence has also been proposed as an enduring human trait by pointing to these behaviors in contemporary chimpanzees.11
At the other end of the spectrum are theories that suggest that cooperation had greater currency in the evolution of human sociality than competition or aggression. Namely, what separated our ancestors from those of contemporary apes was their liberation from primitive limbic system responses to external stimuli and the attendant modulation of hormonally driven behaviors. Current evidence suggests that cortical expansion and a reorganization of brain function was selected for among early hominins, along with the corollary evolution of behavioral plasticity. The increasing ability to interpret stimuli in light of past experience and to apply reasoned, nuanced responses provided hominins with the necessary social tools for empathic and cooperative behaviors. In short, the success of our ancestral lineages relied on the ability to create win-win rather than win-lose scenarios. As recently noted by Clancy (2017), the emergence of our genus may be more accurately described as “survival of the friendliest.” Survival and reproductive success came to those who learned how to get along and to modify their strategic alliances to meet the challenges of changing environmental conditions. This perspective will be favored here.
While behavioral plasticity greatly expanded the social repertoire of early hominins, it did so without sacrificing the option for outlier responses. Humans are capable of both extreme empathy and extreme violence. Where threats to the welfare of offspring or access to critical resources present themselves, limbic system behaviors may rise to the occasion. Such responses, however, should not be regarded as the essence of human nature, nor as a rationalization for the inevitability of human aggression, warfare, or systems of inequality. What is innate is our ability to gauge responses appropriate to stochastic events. If negative or defensive behaviors have become more frequent in the Holocene and Anthropocene epochs, so too, perhaps, have the environmental conditions that trigger this ancient survival response.
Science and Storytelling
Theories on the nature of human nature and societal origins have always been an odd mix of empirical data and fanciful storytelling. I still have vivid memories of a lecture I attended in the 1960s in which my anthropology professor took a stumbling, bent-knee stroll across the stage to demonstrate the typical locomotion of ancient man. The fact that the speaker’s cranial morphology had strikingly Neandertaloid characteristics only served to add to the perceived drama and authenticity of the performance. Subsequent discoveries of additional, nonarthritic Neanderthal skeletons, of course, quickly put this misconception to bed. But not all notions on what life was like on the long road to humanity are so easily tested and modified. In fact, most theories are forced to address many open questions about the course of human evolution, the answers to which will probably remain unknowable.
Why is this? The tangible evidence we have in hand to trace our evolutionary pathway is fragmentary, and may remain so. A tooth here, a tibia there, and if we’re lucky, a skullcap or a complete infracranial skeleton. Exceptional finds, such as the multiple skeletons recently unearthed from the Dinaledi Chamber, South Africa, while enlightening, often pose more questions than answers.12 And so it goes with other sources of data. Geology and paleoecology tell us something about the earth’s past climate and physical environment, but also highlight the prospect that many ancient occupation sites may have been forever lost to rising sea levels. Stone tools give hints about how early humans made a living, but other components of ancient toolkits that could provide major insights, such as items made of wood, bone, and fiber, have long since turned to dust. Similarly, contemporary primates provide glimpses of ourselves and perhaps of a common ancestor, but differ from our proto-human forebears in ways we can only imagine.
And imagine we do. Evolutionary biologists and paleoanthropologists struggle to assemble a complex human-origins puzzle that has unknown dimensions and many missing pieces. Consequently, scientists use their imagination and regularly make up stories (aka models) that paint a more complete picture from the fragments they possess. Multiple stories can be generated from the same evidence or set of facts, and the relative veracity of their competing plots is vigorously debated. A select few, however, are inevitably elevated to the status of academic dogma. These stories are told and retold for decades, and may gain traction for reasons beyond the evidence presented, such as the author’s reputation or the extent to which their conclusions correspond to prevailing cultural stereotypes or popular views of what constitutes “common sense.” But, ideally, dogma is eventually challenged and replaced with new ideas and syntheses that take us closer to an understanding of our roots.
One of the primary challenges facing human-origins storytellers has been the intrepid duo of ethnocentrism and “anthropodenial.”13 Nothing offends scientists more than the suggestion that they approach their subject with less than an open mind. But scientists are human, and humans are creatures of their own culture. When it comes to visualizing what ancient peoples were like, theorists are notorious
