RESOLVING THE PUZZLE
Even at this early stage in our understanding of what baby humans and other apes do spontaneously and what they do in response to social invitations from others, the revelations coming out of Kyoto and elsewhere demonstrate beyond question that other apes have the rudimentary neural equipment to seek out eyes and faces, and they register information about the expressions they see there sufficiently for at least some baby apes to imitate them. Nevertheless, after a while nonhuman ape babies seem no longer interested in this activity and differ from humans in this respect. Human infants either continue to develop and perfect imitative abilities or else (like chimpanzees) abandon the early imitative game and begin to develop a different repertoire of imitative properties.
Like early hominins, the ancestors of these laboratory chimpanzees would have benefited from being able to engage, imitate, and learn from others. After all, the common ancestors of chimpanzees and humans probably hunted in groups. They also bore offspring who would have benefited from being able to learn faster from mothers sensitive to their struggles. Ancestral apes would surely have benefited from being better at guessing what someone else intended—from being better able to read the mental states of apprentices as well as of social competitors or potential allies. Yet as they grow up, other apes remain mired in their immediate desires and needs, leaving us to ponder why Mother Nature did not favor better and better mind readers among the ancestors of modern chimpanzees as well as among our own. How did it happen that eagerness to enter into the mental and emotional states of others and engage them developed in one line of apes but not the other?
The fact that other apes are born with the equipment to engage and imitate others but soon lose interest in doing so leaves unresolved much about the original “Why us and not them?” question. What was it about the rearing conditions of infants in the genus Homo that led to the evolution of more persistent and sophisticated monitoring of group members, of seeking out and gazing into the faces of others, reading their expressions, and gleaning information about their mental states? And what was the payoff? How did such gifts enhance the survival of their possessors? Right from birth, humans develop (as the psychiatrist Daniel Stern likes to say) “in a soup of other people’s feelings and desires.”85 So just what were the special ingredients in that soup?
Of the handful of psychologists who actually spend time pondering what life was like for youngsters millions of years ago, most take for granted that early hominin infants were cared for in the same way as chimpanzees, gorillas, orangutans, and bonobos are today—that is, exclusively by their mothers. This has been a fundamental tenet of “attachment theorists,” as we will see in Chapter 3. Until recently, it is certainly what I believed as well. However, in the next chapter I explain why—in spite of the many similarities—chimpanzees and other nonhuman apes are not the appropriate prototypes to use when reconstructing early hominin childcare.
In the next two chapters I review the many different ways that infant primates are cared for, and I contrast observed infant care among wild Great Apes with the childcare practices of people still living as nomadic hunters and gatherers. These observations make clear that infants in foraging societies confront challenges unlike those faced by any other apes. I will argue that this was probably the case among our hominin ancestors as well, although the existence of such different modes of childcare and their implications for answering the question “Why us and not them?” have long been overlooked. So what were the main differences in the ways hominin and other ape infants were reared?
3
WHY IT TAKES A VILLAGE
We can do without extended families about as easily as we can do without vitamins or essential minerals.
—Kurt Vonnegut (2006)
Every family has secrets. The secret that concerns us here has to do with the taxonomic subfamily Homininae, our bipedal ape ancestors, and dates back millions of years. Fossilized fragments are all that is left of the skeletons in this closet. Yet each of the six billion living descendants from a single hominin line from this subfamily is heir to an ancient legacy endowing them with a penchant for cooperation rarely expressed in other members of the family Hominidae. No other ape, nor any gorilla, chimpanzee, or bonobo, is anything near as good as humans at guessing what others want, or as eager to understand why they might want what they want. Humans alone exhibit spontaneous impulses to share with others and are routinely eager to help.
Much has been written about the large-brained bipeds who buried their dead in elaborate graves, envisioned what stone tools should look like before they crafted them, and left pictographs on cave walls. Remains of anatomically modern people with skulls and bones indistinguishable from those of people today do not appear in the paleontological record before 200,000 years ago. Based on genetic evidence, all humans on earth today descend from a common ancestor that lived in Africa between 50,000 and 150,000 years before the present, and these were the first anatomically modern people who began to think symbolically and use language, possibly a language containing some of the click sounds that can still be heard today among San and Hadza-speakers.1
From an evolutionary perspective, anatomically and behaviorally modern humans are remarkably recent. However, I am convinced that emotionally modern humans date back much further. By emotionally modern I mean bipedal apes born with giving impulses and empathic, intersubjective aptitudes profoundly different from those we see in chimpanzees today—people preadapted to get along with one another even when crowded together on an airplane. Such hominins, I suspect, emerged in Africa hundreds of thousands of years before inventive, symbol-generating, and talkative humans did.
In Chapter 2, I explained that other primates possess neural machinery for imitation and at least a rudimentary capacity to identify with others. The common ancestor of modern humans and chimpanzees presumably also had every incentive to evolve a sophisticated theory of mind and would have benefited from ever-shrewder and more Machiavellian intelligence or from enhanced pedagogical capacities, yet natural selection never favored their acquisition. What happened, then, in the line leading to the genus Homo to favor evolution of these traits? In this chapter and the next I hypothesize that novel rearing conditions among a line of early hominins meant that youngsters grew up depending on a wider range of caretakers than just their mothers, and this dependence produced selection pressures that favored individuals who were better at decoding the mental states of others, and figuring out who would help and who would hurt.
It is often asserted that early hominins were selected for a better mind-reading capacity because it would prepare youngsters to acquire culture, or because it would make humans better at coordinating complex activities.2 Sounds good—except that natural selection, lacking foresight, does not work that way. Blindly groping along with no particular end in view, Mother Nature pays no heed to future benefits such as being better able to generate culture or coordinate large-scale activities. Directional selection favoring improved mind reading required immediate payoffs. Individuals a little bit better at interpreting someone else’s mental state and engaging with them emotionally had to have a better chance than groupmates of surviving and reproducing in the here-and-now. What other apes apparently lacked was an environment in which the components of mind reading and sharing could first develop and then be subjected to selective pressures that favored their possessors.
So what sort of environment would provide already clever and manipulative, highly social (but also highly selfish) apes the opportunity, first, to develop intersubjective abilities right from a formative early age and, then, to benefit from them? In what sort of environment would natural selection actually favor those who were just a little bit more inclined to share? In this chapter I will summarize evidence for thinking that hominin infants must have been reared differently from any other ape. By possibly as early as 1.8 million years ago, hominin youngsters were being cared for and provisioned by a range of individuals in addition to their
mothers, and these rearing conditions set the stage for the emergence of an emotionally more modern ape. Long before our ancestors evolved into big-brained, anatomically modern humans, early hominins were being reared by alloparents as well as parents. Once outed, this long-hidden secret in our family closet requires us to consider exactly what roles these hitherto unacknowledged benefactors played.
It was the end of the twentieth century before evolutionary anthropologists like myself began to consider just how hard it would have been for foragers to rear surviving children, and then to piece together disparate strands of evidence indicating that the help of group members in addition to the genetic parents was absolutely essential for the survival of infants (birth to weaning) and children (weaning to nutritional independence) in the Pleistocene. The need for alloparental succor transformed the selection pressures that shaped our species, and in doing so altered the way infants developed and then the way humans evolved. Like protagonists in a Dickens novel (think of the convict Magwitch and what his anonymous legacy did for Pip’s “great expectations”), these secret benefactors—whose identities we had never even considered before—completely transformed human prospects, including our own lives. But to tell this story, I need to begin at the beginning, with mothers.
MOTHER-CENTERED BEGINNINGS
Let me be clear. None of the family secrets revealed here challenges the central importance of mothers. With the emergence of the first mammals some 200 million years ago, babies were born dependent on nurture from one other individual—their mother, who kept them safe, warm, and milk-fed. Bonds between mother and infant were fundamental to the evolution of the ways creatures like ourselves smell, hear, remember, sense the nearness of, and feel comforted by those close to us. Absent mammals and minus mothers, we would not be groping for terms to express affiliative emotions or need a word like “love” to describe the ties that bind one intimate to another.
Of all the attachments mammalian babies form, none is more powerful than that between baby primates and their mothers.3 The emotional ties that bind ape mothers to their infants and infants to their mothers are unusually long-lasting. Under natural conditions, an orangutan, chimpanzee, or gorilla baby nurses for four to seven years and at the outset is inseparable from his mother, remaining in intimate front-to-front contact 100 percent of the day and night. The earliest a wild chimpanzee mother has ever been observed to voluntarily let a baby out of her grasp is three and a half months.4 Among wild orangutans, half a year elapses, five months at the very least, before a mother allows any other individual, even her own older offspring, to hold her baby.5 A baby ape’s earliest education about the world comes from his relationship with this utterly significant other, his compulsively possessive, highly reliable and responsive mother. His or her mother was every ape’s first and only source of warmth, locomotion, provisioning, and safety, as well as, for months on end with only an occasional glance at others, the sum total of each infant’s social world. Few if any baby apes would have had opportunities to engage and imitate others, much less benefit when they did.
In fact, this continuous-care-and-contact mothering characterizes only about half of the roughly 276 species of living primates, though it includes all four nonhuman Great Apes and many species of Old World monkeys such as the very-well-studied and much-written-about rhesus macaques and savanna baboons.6 The constant care provided exclusively by mothers in these species is due largely to the possessiveness of mothers, not to lack of interest from would-be babysitters. In all primates, other group members (most often subadult females) are attracted to and eager to touch and hold new babies. The mother herself is the limiting factor who determines whether or not they succeed, and in the case of wild apes, the mother is adamant that they will not. Of all continuous-care-and-contact primate mothers, none are more intransigently possessive than Great Apes—a fact, alas, known all too well to poachers. The way to capture a baby gorilla or orangutan is, first, shoot the mother.
Mothers in roughly half of the species in the order Primates remain in continuous contact with their babies for the first weeks or months of life. This orangutan mother will not be out of touch with her baby even for an instant until five to six months after his birth, and the baby will continue to nurse until around age seven. (Tim Laman)
Like many mammals, a Great Ape female near the end of pregnancy grows restless.7 An orangutan mother-to-be builds and rebuilds her sleeping nest, moves about, anxiously checks and rechecks her environs. Prior to birth, the near-term chimpanzee female moves away from groupmates and seeks seclusion. Minutes after birth, possibly while the mother is still consuming the placenta, the tiny, spidery newborn ape on the ground beside her will catch hold of her hairy belly and pull himself aboard, or else the mother herself will pick the newborn up.
The neonate clings to his mother as if his life depends on it, which it does. In the forests and savannas where primates evolved, separation means early death from either predation or starvation. Yet despite their Velcro-like grasp, a newborn chimpanzee or gorilla’s finger-and-toe-hold can be tenuous. Newborns are so poorly coordinated that they can grip tight for only minutes at a stretch, so a mother needs to constantly reach down to readjust her baby or help him gain access to a nipple. Often a mother will walk three-legged or, if climbing vertically, prop the baby up using one or both thighs. Hours or days after birth when the mother rejoins her community, she holds her newborn close, rebuffing every attempt to touch him, wrapping her arms about him and turning her broad, hairy back on would-be nursemaids, folding her body over the baby, foiling access. The awkwardness of this enterprise notwithstanding, ape mothers are unfailingly responsive to infant needs. At the slightest signal of discomfort, the mother reaches down to reposition her burden. As one observer of wild orangutans, Carel van Schaik, put it, the mother responds to every wriggle, every whimper “with the attentiveness of a private nurse and the patience of an angel.”8
Many mammalian mothers can be surprisingly selective about which babies they care for. A mother mouse or prairie dog may cull her litter, shoving aside a runt; a lioness whose cubs are too weak to walk may abandon the entire litter “with no attempt to nudge them to their feet, carry them or otherwise help.”9 Some mammals (and this includes humans) even discriminate against healthy babies, if they happen to be born the “wrong” sex. But not Great Ape or most primate mothers. No matter how deformed, scrawny, odd, or burdensome, there is no baby that a wild ape mother won’t keep. Babies born blind, limbless, or afflicted with cerebral palsy—newborns that a hunter-gatherer mother would likely abandon at birth—are picked up and held close. If her baby is too incapacitated to hold on, the mother may walk bipedally or tripedally so as to support the baby with one hand.10
The primatologist Sarah Turner, who is studying a population of Japanese macaques known for its high prevalence of birth defects, observed a particularly extreme case, a newborn with neither hands nor legs. And yet, as she wrote to me, “His mother carries him everywhere and holds him up to nurse when he can’t reach her nipple.”11 Had local people not fed these monkeys (it was a free-ranging but provisioned and also protected, largely predator-free population), the mother would not have been able to constantly assist her handicapped infant to stay aboard and still remain fed and safe herself. But there is no question that she would have tried.
Monkey and ape mothers rarely discriminate based on a baby’s particular attributes, as some human mothers do. Except perhaps for those born very prematurely, babies are cared for (and carried) almost no matter what. Even if her baby dies, the mother will continue to carry the desiccated corpse about for days, as this langur mother is doing. (S. B. Hrdy/AnthroPhoto)
Maternal devotion in the human case is more complicated. A woman undergoes the same endocrinological transformations during pregnancy as other apes. At birth, her cortisol levels and heartbeat reflect just how sensitive to infant cues she has become.12 But whereas the nonhuman ape mother undiscriminatingly accepts any infant born to h
er without taking into account physical attributes, the human mother’s devotion is more conditional. A newborn perceived as defective may be drowned, buried alive, or simply wrapped in leaves and left in the bush within hours of birth.13 “Defective” may mean anything from having too many toes to too few. It may mean being born with a deformed limb or at a very low birthweight, coming too soon after the birth of an older sibling, or having some culturally arbitrary or other affliction such as having too much or too little hair, or being born the wrong sex.
Humans last shared a shaggy, arboreal common ancestor with compulsively possessive orangutan mothers 14 million years ago, with gorillas closer to 8 million. We shared a common ancestor with continuous-care-and-contact chimpanzee and bonobo mothers a mere 6 million years ago or so.14 At some point in the intervening eons hominin mothers lost the hair that other ape babies cling to. The best available estimate (based on genetic evidence indicating when our ancestors exchanged a type of body louse that lives in fur for one that lives in pubic hair) suggests that hominins started to lose much of their body hair by 3.3 million years ago.15 This meant that a newborn whose inexperienced first-time mother did not immediately pick him up would not have had the option of grabbing a scraggly foothold until his mother began to respond to him. With hair loss, mothers and babies alike probably could have used help more than ever.
Although human infants are born with the same grasping reflex that other apes have, they lose it shortly after birth. Furthermore, unlike any other ape, a mother in a hunter-gatherer society examines her baby right after birth and, depending on its specific attributes and her own social circumstances (especially how much social support she is likely to have), makes a conscious decision to either keep the baby or let it die. In most traditional hunter-gatherer societies, abandonment is rare, and almost always undertaken with regret. It is an act no woman wants to recall, a topic ethnographers must tiptoe around gingerly. Typically, interviewers will broach the subject indirectly, asking other women rather than the mother herself.16 Back when the !Kung still lived as nomadic hunter-gatherers, the rate of abandonment was about one in one hundred live births. Higher rates were reported among people with strong sex preferences, as among the pre-missionized Eipo horticulturalists of highland New Guinea. Forty-one percent of live births in this group resulted in abandonment, and in the vast majority of cases the abandoned babies were newborn daughters whose mothers hoped to reduce the time until a son might be born.17
Mothers and Others Page 8
