Many systematists now place Homo erectus along with all the other bipedal apes into the tribe Hominini. This new term “hominin” replaces the older term “hominid” because in the new classification other apes such as chimpanzees fall, along with humans, into the family Hominidae, as in “We are all hominids now.” The fossil hominins depicted in this family tree include Australopithecus, Homo habilis, Homo erectus, and Homo heidelbergensis, but there are many others, not shown, and no doubt still others not yet discovered. As illustrated here, modern humans probably all descended from an African branch of Homo erectus (also called Homo ergaster) that evolved around 1.8 million years ago. This diagram, originally prepared by evolutionary anthropologist Richard Klein, is adapted here from Henry McHenry (2009).
So here we have a footloose hominin that managed to persist—albeit initially just barely—for 1.6 million years, eight times longer than Homo sapiens has been on this earth. Yet there were probably never very many of them. Unlike the case of other large mammals traversing savannas and mixed woodland-savanna habitats a million years ago, it takes tremendous effort and considerable luck to find even a single skull belonging to the African branch of Homo erectus. My guess is that one reason for the scarcity of such finds is that the creatures themselves were scarce. It was probably not until 80,000 or so years ago in Africa, and perhaps 50,000 years ago in Europe, that human populations began to expand. Prior to that, Paleolithic populations would have been small and dispersed. In total, they would have numbered in the tens of thousands, and the resources they needed would often have been widely distributed as well as unpredictable.48 When vegetable food or game were available, luck, skill, and the effort expended to harvest them would have mattered more than fighting for them.
Without kin and as-if kin to help protect and especially to help provision them, few Pleistocene children could have survived into adulthood. The fact that children depend so much on food acquired by others is one reason why those seeking human universals would do well to begin with sharing. Nevertheless, in Darwinian circles these days the most widely invoked explanation for how humans became so hypersocial is to stress how helpful within-group cooperation is when defending against or wiping out competing groups. We are told again and again that “the human ability to generate in-group amity often goes hand in hand with out-group enmity.”49 Such generalizations are probably accurate enough for humans where groups are in competition with one another for resources, but how much sense would it have made for our Pleistocene ancestors eking out a living in the woodland and savannas of tropical Africa to fight with neighboring groups rather than just moving?
Small bands of hunter-gatherers, numbering 25 or so individuals, under conditions of chronic climatic fluctuation, widely dispersed over large areas, unable to fall back on staple foods like sweet potatoes or manioc as some modern foragers in New Guinea or South America do today, would have suffered from high rates of mortality, particularly child mortality, due to starvation as well as predation and disease. Recurring population crashes and bottlenecks were likely, resulting in difficulty recruiting sufficient numbers. Far from being competitors for resources, nearby members of their own species would have been more valuable as potential sharing partners. When conflicts did loom, moving on would have been more practical as well as less risky than fighting.50
Nevertheless, from the early days of evolutionary anthropology to today’s textbooks in evolutionary psychology, the tendency has been to devote more space to aggression and our “killer instincts” or to emphasize “demonic” chimpanzeelike tendencies for males to join with other males in their group to hunt neighboring groups and intimidate, beat, torture, and kill them.51 No doubt our Pleistocene ancestors experienced jealousy, competed for reputation, and harbored grudges or desires for retribution that occasionally escalated into mayhem. Homicides among hunter-gatherers are well documented, often crimes of passion involving women. But such killings tend to involve individuals who know each other rather than warfare between adjacent groups. In spite of abundant evidence documenting intergroup conflict over the past 10,000 to 15,000 years, there is no evidence of warfare in the Pleistocene. Such absence of evidence is not evidence of absence, but it helps to explain why many of those who actually study hunter-gatherers are skeptical about projecting the bellicose behavior of post-Neolithic peoples back onto roaming kin-based bands of hunter-gatherers, and why some anthropologists refer to the Pleistocene as the “period of Paleolithic warlessness.”52
I am not about to argue that competition is unimportant. We are primates, after all. But what worries me is that by focusing on intergroup competition, we have been led to overlook factors such as childrearing that are at least as important (in my opinion, even more important) for explaining the early origins of humankind’s peculiarly hypersocial tendencies. We have underestimated just how important shared care and provisioning of offspring by group members other than parents have been in shaping prosocial impulses.
I am assuming that prior to the Neolithic, when around 12,000 or so years ago people began to settle down and produce rather than just gather food, band-level societies would have gone to the same lengths to avoid outright conflicts and to maintain harmonious relations as do the African hunter-gatherers studied by twentieth and twenty-first century ethnographers. Acutely aware of how divisive and potentially dangerous status-striving and self-aggrandizing tendencies can be, hunter-gatherers almost everywhere are known for being fiercely egalitarian and going to great lengths to downplay competition and forestall ruptures in the social fabric, for reflexively shunning, humiliating, even ostracizing or executing those who behave in stingy, boastful, or antisocial ways.53
When murder does occur, group members intervene and customs are invoked that help keep violent apelike instincts from escalating and to prevent homicides from spiraling into wider blood feuds or intergroup fighting.54 People living in band-level gathering and hunting societies behave as if they understand that their survival and that of their children depend on others, that without kin and as-if kin to help keep children safe and fed, their communities cannot survive. Maintaining social contacts and exchanging goods and services, even with those who are not particularly close relatives, is something humans are emotionally and temperamentally peculiarly well equipped to do, especially when compared with other apes.
Yet textbooks in fields like evolutionary psychology devote far more space to aggression, or to how men and women competed for or appealed to mates, than they do to how much early humans shared with one another to jointly rear offspring.55 Even when human hypersociality is noted, explanations tend to emphasize between-group competition rather than how difficult it was to ensure the survival to breeding age of costly, slow-maturing children. Yet as this book will make clear, without shared care and provisioning, all that inter- and intragroup strategizing and strife would have been—evolutionarily speaking—just so many grunts and contortions signifying nothing.
PAN-HUMAN COMPARISONS
The Great Apes known as common chimpanzees (Pan troglodytes) lack the giving impulses typical of people. Reflexively xenophobic, either sex is more likely to attack than to tolerate a stranger of the same sex. However, members of another Great Ape species, bonobos (Pan paniscus, sometimes called pygmy chimpanzees), are more tolerant and relaxed around conspecifics. Bonobos are temperamentally more similar to humans in this respect than common chimpanzees are. Genetically, however, neither species of chimpanzee is closer to humans than the other is. Humans shared a common ancestor with these other two apes six or so million years ago.
Although genetically equidistant from humans, the two species of the genus Pan diverged from each other only in the past two million years. No one knows whether bonobos derived from a more chimpanzeelike ancestor or the other way around. Yet because Pan troglodytes has been intensively studied for much longer than Pan paniscus, and also because their dominance-oriented and aggressive behavior, including murderous raids on neighboring groups, more nearly con
forms to widely accepted stereotypes about human nature, there is a bias toward viewing common chimpanzees as the template for the genus, while dismissing bonobos as some eccentric offshoot. As a result, the violence-prone temperament assigned to male Pan troglodytes is routinely projected back onto our Paleolithic ancestors.56
Even though no one knows whether common chimpanzees or bonobos provide the better model for reconstructing particular traits among our hominin ancestors, if I had to bet on which species made the more plausible candidate for reconstructing a line of apes with the potential to evolve extensive sharing, particularly care and provisioning of young by group members other than parents (known as alloparents),* I would bet on bonobos. Based on laboratory experiments, bonobos appear to be more gregarious, and bonobo females in particular are temperamentally better suited to tolerate others and to learn to coordinate their behavior with them.57 In the wild as well as in captivity, bonobos tend to be more peaceful and sociable than common chimpanzees. Thus far, bonobos have not been observed to stalk or kill neighbors, although we know too little to say they never do. What we do know is that when bonobo communities meet at the border of their home ranges or when strange males try to immigrate into a group, the responses vary with the circumstances. Individuals may exhibit hostility or they may intermingle peaceably. Males and females may even consort with one another.58 Opportunistic copulations with strangers are facilitated because female bonobos are nearly continuously sexually receptive and exhibit red sexual swellings during most days of their estrous cycles, with no specific visual advertisement at ovulation.59
Both in captivity and in the wild, bonobos share more readily than chimpanzees do, and when begged by youngsters, group members of both sexes may provide food to the offspring of their female friends.60 In general, bonobos seem more eager to cooperate and may be more adept at reconciliation after conflict.61 They nimbly and routinely combine vocalizations, facial expressions, and gestures for effective, flexible communication.62 Yet bonobos rarely exhibit the spontaneous giving impulses commonly observed in very young human children.
Among people, these giving impulses, combined with chimpanzees’ and the other Great Apes’ rudimentary capacity for attributing mental states and feelings to others, lead humans of all ages to routinely seek out opportunities to engage with other individuals. The kind of interindividual tolerance so typical of humans suggests that even before people had language to discuss things, prehuman or early human apes were equipped with the capacity to identify with others and engage with them in ways that avoided fights.63 These hominins were already emotionally different from other apes. This is where the homology between humans and “demonic” chimpanzees breaks down. In what follows I will argue that as long as a million and a half years ago, the African ancestors of Homo sapiens were already emotionally very different from the ancestors of any other extant ape, already more like the sort of ape one would prefer to travel with in a confined space.
GIVING IMPULSES
A human child is born eager to connect with others. In a gathering and hunting society, that child also would become accustomed to being cared for and fed by others in a nurturing environment.64 Before Ju/’hoansi children are a year old and able to talk, they are already socialized to share with their mother and with other people as well. Among the first words a child learns are na (“Give it to me”) and i (“Here, take this”).65 Polly Wiessner recalls an old woman cutting off a strand of ostrich eggshell beads from around her grandchild’s neck, washing the beads off, and then placing them in the child’s hand to present (however grudgingly) to a relative. After the lesson of giving was accomplished, the child was given new beads. This routine was repeated until, by about age nine, children themselves initiated giving. By adolescence, a fully socialized donor expands his or her hxaro contacts further and further afield. The fearful prospect of disrupting the fabric of relationships that sustained the lives of our ancestors acted as a perpetual lid, constraining conflict.
Among nonhuman apes, however, sharing is uncommon, neither spontaneous nor reciprocal. An alpha male chimpanzee grasping the carcass of a monkey he just killed may allow a sexually receptive female or close male associate to rip off a piece, but this is more like “tolerated theft” than a real gift.66 Rarely have fieldworkers seen a wild chimpanzee extend a preferred section of meat, even to his best ally. Yet humans routinely offer preferred foods to others—the best hospitality we can possibly provide. A mother chimpanzee or orangutan will tolerate her youngster taking a desirable scrap of the food she is eating, but she rarely takes the initiative in offering it. If a Pan troglodytes mother does extend her hand with a tidbit, she will most likely proffer a stem or some other unpalatable plant part that she herself does not particularly want to eat.
Although bonobos may be more tolerant about food sharing than common chimpanzees, no one would mistake their behavior for gift-giving. The majority of sharing involves plant foods rather than meat and usually occurs between two adult females or an adult female and an infant—her own or the infant of one of her female allies or associates. Instead of being offered some delectable treat, infants merely have license to take food in the possession of allomothers. When an adult bonobo shares food with another adult, almost invariably the offer is in reaction to begging gestures similar to those infants make.67 Not long ago, at a bonobo study site in the Congo called Lomako, researchers watched as females gathered to feed on the corpse of a duiker. Among common chimpanzees, males are dominant over females and control access to meat; but among bonobos, females are dominant to males and control the flow of food. On this particular occasion, all three infants present could pick at the carcass and were also permitted to casually take pieces of meat from the hands and mouths of adults, but this is as generous as things got.68
These photos were extracted from a video made in the middle of the twentieth century by the pioneering human ethologist Irenäus Eibl-Eibesfeldt. He traveled around the world with a specially designed camera whose right-angle lens could be aimed in one direction while recording images from another. This allowed him to compile a precious archive of candid photographs illustrating infant care in traditional societies such as the !Xo, G/wi San, and Himba of southern Africa, the Eipo of West Papua, the Trobrianders of Papua New Guinea, and the Yanomamo of Venezuela. Picking up where Darwin left off in his 1872 classic The Expression of Emotions in Animals and Man, Eibl-Eibesfeldt sought to demonstrate the universality of human facial expressions, gestures, and emotions. Here, a Yanomamo toddler goes over to her playmate, carrying two large leaves, and sits down beside the other girl. Unnoticed by her friend (second frame), the little girl swipes one of the leaves and hides it behind her. But when her playmate spontaneously presents her with the other leaf as a “gift” (third frame), she returns the “stolen” leaf, as if aware that generosity must be reciprocated. Such is the power of gift-giving, right from an early age, even before language and terms to describe the giving impulse develop. (I. Eibl-Eibesfeldt/Human Ethology Archives)
Where gift-giving does occur in the animal world, it tends to be a highly ritualized, instinctive affair, as when a male scorpion fly offers prey to a prospective mate as a “nuptial gift” to induce the female to mate with him, or when male bowerbirds or flightless cormorants bring some eye-catching object to a fertile female to use in decorating her nest. Cases of nonhuman animals voluntarily offering a preferred food in the true spirit of gift-giving are rare, except in species which, like humans, also have deep evolutionary histories of what I call cooperative breeding, where there is shared care and provisioning of young.69
Among the higher primates, humans stand out for their chronic readiness to exchange small favors and give gifts. Donors often take the initiative, actually seeking opportunities and expending inordinate thought and effort to select “just the right gift,” the one most likely to suit the occasion or to impress or appeal to the recipient. Humans spontaneously notice and keep track of the smallest detail about their exchanges.70
Custom, language, and personal experiences shape the specifics, but the urge to share is hard-wired, and neurophysiologists are getting to the point where they can actually monitor, if still only crudely, the pleasure humans derive from being generous, helping, and sharing.71
This should not come as a surprise. As early as a million years ago, archaeologists tell us, hominins were transferring materials between distant sites. By the Middle Stone Age (50,000 to 130,000 years ago), the type and quantity of such transfers indicates the existence of long-distance exchange networks.72 We can say with considerable confidence that the sharing of material objects, and with it a degree of intersubjectivity that would make such sharing a satisfying activity, go far back in time. Yet as universal and presumably ancient in the hominin line as sharing appears to be, a comparable giving impulse is not present in other apes. Whereas competitiveness and aggression are fairly easy to understand, generosity is both less common and more interesting, but from an evolutionary perspective far harder to explain.
A four-and-a-half-year-old Himba girl urges her cousin to have a bite of her snack. Young children are eager to give and readily learn to share, even though they sometimes may need some prodding. (I. Eibl-Eibesfeldt/Human Ethology Archives)
Mothers and Others Page 3