Mothers and Others

by Sarah Blaffer Hrdy

  What about locomotion as the distinguishing trait? A key criterion of humanness, upright walking on two legs, bit the dust with the discovery of a fossilized trail of bipedal footprints left in volcano ash by australopithecines—apes with brains no bigger than a chimpanzee’s—some four million years ago. Fossilized footprints together with fossilized skeletal remains made it clear that these long-armed, small-brained, extraordinarily chimplike creatures were walking upright millions of years before the emergence of the genus Homo.23

  Bipedality is not what makes us human, and as clever as we think we are, the really big differences between chimpanzees and humans do not lie in the realm of basic spatial cognition or memory.24 Apart from language, where humankind’s uniqueness has never been in serious dispute, the last outstanding distinction between us and other apes involves a curious packet of hypersocial attributes that allow us to monitor the mental states and feelings of others, as scientists at the Max Planck Institute of Evolutionary Anthropology have recently suggested.

  This institute is the premier place for studying psychological traits possessed by humans and other apes. Part of its ambitiously interdisciplinary research project is housed in a large building in the heart of the historic German city of Leipzig. Its offices and laboratories are filled with psychologists, behavioral ecologists, primatologists, and geneticists, who in a technical tour de force were recently able to extract DNA from extinct Neanderthals and compare it with that from modern humans. Research on children’s cognitive development goes on here as well. The other branch of the institute is located a short distance away, in a sprawling zoological garden that is home to social groups of gorillas, chimpanzees, bonobos, and orangutans. Special laboratories enable scientists to conduct experiments on ape cognition, including recent experiments showing that bonobos and orangutans can plan ahead. All five species—human children and the four Great Apes—are being studied simultaneously using comparable methods, with spectacular results.

  In 2005 Michael Tomasello, the American-born leader of the Max Planck team, proposed a new dividing line between humans and nonhuman apes. “We propose,” he and his colleagues announced, “that the crucial difference between human cognition and that of other species is the ability to participate with others in collaborative activities with shared goals and intentions.”25 For the moment, this trait, along with our extralarge brains and capacity for language, marks the new dividing line separating our natures from those of other apes. Accordingly, “human beings, and only human beings, are biologically adapted for participating in collaborative activities involving shared goals and socially coordinated action plans.”26 Only among humans do we find large-scale cooperative endeavors involving people who are not necessarily close kin. Only humans, for example, can fan out around an encampment, gather building materials, consciously register the mental blueprint someone else has in mind, and chip in to help construct a shelter.

  During the dry season in central Brazil, Kayapó men wade into the shallow currents of the Xingu River where they release a fish poison by beating bundles of a plant called timbo. Stunned or suffocated by the timbo sap, fish float to the surface and are easily gathered by women and children who wade in with baskets at the water’s edge. Such high-value food sources were out of reach of our prehominin ancestors but became accessible once hominins with stone-age technologies began to understand one another’s goals well enough to coordinate complex activities. (Joan Bamberger)

  Humans “are the world’s experts at mind reading,” far more “biologically adapted” to collaborate with others than any other ape, Tomasello stresses. To him, these aptitudes are nearly synonymous with our special ability to perceive what others know, intend, and desire.27 Human infants are not just social creatures, as other primates are; they are “ultrasocial.”28 Unlike chimpanzees and other apes, almost all humans are naturally eager to collaborate with others. They may prefer engaging with familiar kin, but they also easily coordinate with nonkin, even strangers. Given opportunities, humans develop these proclivities into complex enterprises, such as collaboratively tracking and hunting prey, processing food, playing cooperative games, building shelters, or designing spacecraft that reach the moon.29

  At some point in the course of their evolution, our ancestors became more deeply interested in monitoring the intentions of others and eager to share their inner feelings and thoughts as well as their mental states. This interest laid the groundwork for the peculiarly cooperative natures that would distinguish these hominins from other bipedal apes and rendered apes in the line leading to the genus Homo what I think of as emotionally modern.30 My goal in writing this book is to understand how such other-regarding tendencies could have evolved in creatures as self-serving as apes are.

  The fact that humans are better equipped to cooperate than other apes does not mean that men do not compete with one another for status or for access to mates, or that women are not also fiercely competitive in the domains that matter to them, striving for desirable mates, local clout, and access to resources for themselves and their children. Such status quests are primate-wide propensities, and, under pressure, conflict boils over into violence. Nevertheless, as Tomasello emphasizes, people’s peculiar eagerness to read and share the feelings and concerns of others, their quest for intersubjective engagement and mutual understanding, provides the underpinning for behaving in a more prosocial way. It is what makes humans so much more desirable as travel companions than other apes are. So where did this human questing for intersubjective engagement come from?

  TO CARE AND TO SHARE IS TO SURVIVE

  The benefits to humans of their other-regarding tendencies have never been in doubt. This mutual understanding provided the foundation for the evolution of cooperative behaviors. Before returning to the perplexing question about origins so central to this book, namely, “How on Darwin’s earth did the stage for such cooperation get set?” I briefly want to remind readers why (once the initial propensities had evolved) being eager to share and willing to cooperate were so critical during the long stretch of time when our ancestors lived as hunters and gatherers. That done, we can return to the question of origins, and ask how mind reading, empathy, and the other underpinnings for higher levels of cooperation became so well developed in one particular line of apes. Still later developments, having to do with the evolution of our unique intelligence, language, and other critical components of human-level cooperation, are beyond the scope of this book. So let’s start with sharing, a quintessentially human trait.

  During the voyage of the Beagle when the young Charles Darwin first encountered the “savages” living in Tierra del Fuego, he was amazed to realize that “some of the Fuegians plainly showed that they had a fair notion of barter . . . I gave one man a large nail (a most valuable present) without making any signs for a return; but he immediately picked out two fish, and handed them up on the point of his spear.”31 Why would sharing with others, even strangers, be so automatic? And why, in culture after culture, do people everywhere devise elaborate customs for the public presentation, consumption, and exchange of goods?

  Gift exchange cycles like the famous “kula ring” of Melanesia, where participants travel hundreds of miles by canoe to circulate valuables, extend across the Pacific region and can be found in New Zealand, Samoa, and the Trobriand Islands. In New Caledonia, giant yams are publicly displayed in the Pilu Pilu ceremonies, while among the Kwakiutl, Haida, or Tsimshian peoples along the resource-rich coast of northwest North America as well as among the Koryak or Chuckchee peoples of Siberia, quantities of possessions are publicly shared and destroyed in elaborate potlatch ceremonies. As I write these words, I am reminding myself to update the long lists of recipients to whom we send cards and boxes of fresh walnuts each Christmas—my own tribe’s custom for staying in touch with distant kin and as-if kin, the creation of which is a specialty of the human species. The point is not merely to share but to establish and maintain social networks, as Marcel Mauss argued in one of an
thropology’s early classics, Essai sur le don (The Gift). This is why dopamine-related neural pleasure centers in human brains are stimulated when someone acts generously or responds to a generous act.32

  One of the earliest in-depth studies of traditional exchange networks was undertaken by the anthropologist Polly Wiessner, who has done extensive fieldwork in Africa and New Guinea. She began her Kalahari research in the 1970s among the San-speaking Ju/’hoansi people, also known as the !Kung or Bushmen, who at that time still lived as mobile gatherers and hunters belonging to one of the most venerable human groups on earth. Genetic comparisons of mitochondrial DNA across extant human populations indicate that ancestors of this relatively isolated population of Khoisan people, along with those of some other remnant foragers in Central Africa, split off from humankind’s founding population at a very early date. Both men and women carry the mitochondrial DNA characteristic of the deepest roots of the African phylogenetic tree from which all modern humans descend.33

  No matter how skilled the hunter, locating and killing prey is a risky enterprise, with unpredictable outcomes. A man can go hunting every day and still come home empty-handed for weeks in a row. A hunter like this Ju/’hoansi man can afford to fail because he can count on a share of fruits, nuts, and tubers gathered by women, and also because other men may have better luck that day. Inherently less of a gamble, gathering still depends on the vagaries of rainfall and fruiting cycles as well as which other creatures get to a particular food source first. (Peabody Museum/Marshall Expedition image 2001.29.363)

  As among our earliest Pleistocene ancestors, Ju/’hoansi women gathered and the men hunted, with communities sharing the fruits of their labors. Over the next thirty years, Wiessner followed the lives of group members even after they were displaced from their traditional foraging grounds. Today, their descendants eke out a living by gardening and herding when they can, subsisting on government handouts or “lying out the hunger”—patiently suffering—when they can’t. When they still roamed across the semi-arid Kalahari, with no way to store food, these people understood that their most important resources were their reputations and the stored goodwill of others.

  The sporadic success and frequent failures of big-game hunters is a chronic challenge for hungry families among traditional hunter-gatherers. One particularly detailed case study of South American foragers suggests that roughly 27 percent of the time a family would fall short of the 1,000 calories of food per person per day needed to maintain body weight. With sharing, however, a person can take advantage of someone else’s good fortune to tide him through lean times. Without it, perpetually hungry people would fall below the minimum number of calories they needed. The researchers calculated that once every 17 years, caloric deficits for nonsharers would fall below 50 percent of what was needed 21 days in a row, a recipe for starvation. By pooling their risk, the proportion of days people suffered from such caloric shortfalls fell from 27 percent to only 3 percent.34

  For those who store social obligations rather than food, unspoken contracts—beginning with the most fundamental one between the group’s gatherers and its hunters, and extending to kin and as-if kin in other groups—tide them over from shortfall to shortfall. Time-honored relationships enable people to forage over wider areas and to reconnect with trusted exchange partners without fear of being killed by local inhabitants who have the advantage of being more familiar with the terrain.35 When a waterhole dries up in one place, when the game moves away, or, perhaps most dreaded of all, when a conflict erupts and the group must split up, people can cash in on old debts and generous reputations built up over time through participation in well-greased networks of exchange.

  The particular exchange networks that Wiessner studied among the Ju/’hoansi are called hxaro. Some 69 percent of the items every Bushman used—knives, arrows, and other utensils; beads and clothes—were transitory possessions, fleetingly treasured before being passed on in a chronically circulating traffic of objects. A gift received one year was passed on the next.36 In contrast to our own society where regifting is regarded as gauche, among the Ju/’hoansi it was not passing things on—valuing an object more than a relationship, or hoarding a treasure—that was socially unacceptable. As Wiessner put it, “The circulation of gifts in the Kalahari gives partners information that they ‘hold each other in their hearts’ and can be called on in times of need.”37 A distinctive feature of human social relations was this “release from proximity.” It meant that even people who had moved far away and been out of contact for many years could meet as fondly remembered friends years later.38 Anticipation of goodwill helps explain the 2008 finding by psychologists at the University of British Columbia and Harvard Business School that spending money on other people had a more positive impact on the happiness of their study subjects than spending the same amount of money on themselves.39

  In her detailed study of nearly a thousand hxaro partnerships over thirty years, Wiessner learned that the typical adult had anywhere from 2 to 42 exchange relationships, with an average of 16. Like any prudently diversified stock portfolio, partnerships were balanced so as to include individuals of both sexes and all ages, people skilled in different domains and distributed across space. Approximately 18 percent resided in the partner’s own camp, 24 percent in nearby camps, 21 percent in a camp at least 16 kilometers away, and 33 percent in more distant camps, between 51 and 200 kilometers away.40

  Just under half of the partnerships were maintained with people as closely related as first cousins, but almost as many were with more distant kin.41 Partnerships could be acquired at birth, when parents named a new baby after a future gift-giver (much as Christians designate godparents), or they could be passed on as a heritable legacy when one of the partners died. Since meat of large animals was always shared, people often sought to be connected with skilled hunters. This is why the best hunters tended to have very far-flung assortments of hxaro contacts, as did their wives.

  Contacts were built up over the course of a life well-lived by individuals perpetually alert to new opportunities. When a parent died, his or her children or stepchildren inherited the deceased person’s exchange partners as well as kinship networks, and gifts were often given at that time to reinforce the continuity, since to give, share, and reciprocate was to survive.42 Multiple systems for identifying kin linked people in different ways, increasing the number of people to whom an individual was related. One kinship system was based on marriage and blood ties, while another involved the name one was given, which automatically forged a tie to others with the same name. These manufactured or fictive kin were also referred to as mother, father, brother, or sister.

  Such dual systems function to spread the web of kinship widely, and since the second system can be revised over the course of an individual’s lifetime, it becomes feasible for a namesake to bring even distant kin into a closer relationship when useful.43 Every human society depends on some system of exchange and mutual aid, but foragers have elevated exchange to a core value and an elaborate art form. People construct vast and intricate terminologies to identify kin and as-if kin, in order to expand the potential for relationships based on trust. Depending on the situation, these can be activated and kept going by reciprocal exchange or left dormant until needed.

  Marriages that Ju/’hoansi partners arranged for their children provided new opportunities to cast the net wider still. At marriage, band members offer gifts to the newlyweds that are then recycled among in-laws. A wife taken by force would be far less valuable than the same woman freely given by in-laws properly compensated and ready to reciprocate. Under conditions of high child mortality, a kinless woman would make a less advantageous mate than one whose family support system was intact, because children without maternal grandmothers and other kin to help nurture them would be less likely to survive. Kinship ties, together with the terminologies and relationships based on the exchange of goods and services that are used to reify them, increase the number of people that one coul
d call upon, share with, count on to reciprocate, go to live with when in need, and elicit help from in rearing one’s young.44 The advantage of casting the net of kinship as widely as possible is presumably why foraging people are far more likely to trace relatedness through both mother and father, as opposed to only one or the other line, as is more typical in the matrilineal or patrilineal descent systems that prevail in nonforaging societies.45

  Archaeological evidence suggests that unilineal—and perhaps especially patrilineal—inheritance systems began to emerge when foragers in habitats rich with marine resources began living more sedentary lives at higher population densities, as they did in coastal South Africa from at least 4,300 years ago. As with most primates, population densities of Paleolithic foragers would have varied across their range, from very low (with less than one person per square mile) to somewhat higher.46

  Consider one of the most successful, widespread, and long-lived of all hominins, Homo erectus, which first emerged around 1.8 million years ago. Some members of this highly variable (or polytypic) species must have migrated out of Africa early on. Fossils from an archaic form of Homo erectus are being unearthed at the Dmanisi site in the Republic of Georgia, with other remnants uncovered in Java, China, and Spain. Indeed, many paleontologists believe that the miniaturized hominins from the island of Flores off Indonesia were similarly left over from one of these early Pleistocene diasporas. As far as we know, all of these early-dispersing populations eventually died out. However, a branch of Homo erectus remained in tropical Africa and continued to evolve there. All humans today descend from this enduring African branch of Homo erectus, which some paleontologists regard as a separate species, Homo ergaster. Whatever we call them, these larger-brained African hominins were our ancestors, giving rise around 200,000 years ago to even-larger-brained Homo sapiens. Sometime afterward, between 100,000 and 50,000 years ago, these anatomically modern humans spread out of Africa, and Homo sapiens began its extraordinary expansion around the world.47