Mothers and Others

by Sarah Blaffer Hrdy

  As it happens, callitrichids do not register color quite the same way colobine monkeys do. Whereas the retinas of apes and Old World monkeys are characterized by three types of cone photoreceptors (trichromacy), marmosets and tamarins, like many New World primates, typically lack trichromacy.29 Thus, while a marmoset baby’s main predators, raptorial birds, would still be able to pick out a flamboyantly colored baby, the signal would be lost on potentially helpful conspecifics—all the costs and none of the benefits. Furthermore, since hawks, eagles, and falcons all originally evolved in South America between 50 and 80 million years ago, New World monkeys have been under pressure from above for a very long time. Under the circumstances, it is perhaps no wonder Mother Nature opted for camo.

  Fancy natal dress is not always advantageous, nor is it always feasible to evolve. The object after all is natal, not fatal, attraction. But in species with color vision, where alloparental attentions do indeed enhance the survival of immatures even by a small degree, over generations the evolutionary advantage of eye-catching natal dress is potentially enormous. There is every reason to assume that distinctive natal coats are biological traits that evolved through natural selection because they increased the reproductive success of the parents who carried genes for them. In humans, however—who recently shared a common primate ancestor with non-infant-sharing apes—the raw material for colorful babies may not have been there, or perhaps time was just too short, or maybe human babies appeal through other means, by being expressive and unusually plump. Humans are born far fatter than other apes are, advertising in this way that they are full-term babies worth keeping.30

  Even though physical traits like coat color typically take many generations to evolve, new behaviors can emerge more swiftly. In the human case, magnifiers of nurturing responses may be culturally introduced by what mothers do to their babies. Perhaps they noticed that babies who were “dressed up” survived better. Hence it is time to examine how the cooperative breeding model alters the way anthropologists interpret some of the curious things that people do to, and with, their babies.

  DRESSING FOR POPULARITY

  Unlike infant-sharing monkeys, human babies are not born wearing fancy natal dress. Their appeal is broadcast by big heads, plump bodies, and, in time, smiles and chortles. Their infantile appeal is in the eye of their beholders, their message designed primarily for very local consumption, their immediate priority being to appeal to their unusually discerning human mothers.31 But other than being a lot less scrawny than other apes are, human babies are not born looking any fancier at birth than an orangutan or chimpanzee baby does. Presumably, the common ancestor of humans and other apes were fairly drab as well. Yet through their actions human mothers have managed to converge on the same sorts of solution to their childcare and posterity problem that infant-sharing monkeys arrived at through the evolution of physical traits. Mothers themselves decorate, arrange, and train their babies in ways that make them more flamboyantly attractive to other caregivers.

  In her richly textured account of “the culture of infancy” in a West African Beng village, the cultural anthropologist Alma Gottlieb describes infant care practices that initially seem puzzling. To Gottlieb, the way the Beng treat their babies seemed so nonsensical that she became convinced that their mode of childcare could be understood only within their peculiar symbolic system. Like many cultural anthropologists, she saw little point in considering evolutionary contexts or adaptive functions.

  At first glance, her prejudice against adaptive explanations in this instance seems well-founded. For Beng mothers engage in some remarkably counterintuitive, maladaptive-seeming behaviors. They force babies to drink water before allowing them access to the breast. They also administer herbal enemas several times a day, and decorate their babies’ faces and bodies with protective painted symbols thought to promote health and growth, as well as to advertise tribal status or identity. Such practices, Gottlieb argues, flow from belief systems specific to the Beng, having to do with the sacredness of water and the origin of babies who enter the world reincarnated from ancestors, and can only be understood within the context of a specifically Beng worldview.

  At first glance, such practices seem to defy common sense and functional explanation. How could enemas and body paint have anything to do with keeping babies healthier or enhancing their survival? If any customs fly in the face of theories about adaptive behavior, surely these do. Symbolic decorations are not going to encourage babies to grow faster or make them healthier, and parasite- and bacteria-laden water forced down a baby’s throat is likely to do the reverse, causing diarrhea. And what use are excretion-promoting enemas when the big problem in this society is malnutrition? Combined with all the other economic and environmental challenges Beng children face—protein shortage, disease, the backbreaking work their mothers must combine with childcare—it is no wonder that nearly all are malnourished and more than 20 percent die before age five.32

  And yet stand back and consider Beng maternal practice in terms of the universal dilemma confronting primate mothers who find themselves torn between heavy subsistence loads and the need to care for infants in the face of high rates of mortality. These are mothers who cannot possibly rear their infants without assistance from others. Next, consider the Beng in the context of a species that must have evolved as a cooperative breeder. Again and again, Gottlieb mentions the “enormous labor demands” on Beng mothers who farm full-time, chop and haul firewood, provide water, do the laundry, and prepare food using labor-intensive methods.33 A woman, especially an undernourished woman with several children, could not possibly manage these tasks without enlisting kin and other villagers to help her care for her infant. As it turns out, each of the seemingly useless cultural practices mentioned above also just happens to make babies more attractive to allomothers.

  “Every Beng mother,” Gottlieb writes, “makes great efforts to toilet-train her baby from birth so as to attract a possible [caretaker] who can be recruited to the job without fear of being soiled. The goal is for the infant to defecate only once or twice a day, during bath time, so as never to dirty anyone between baths, especially while being carried.”34 It is to make a baby more easily comforted by a nonlactating allomother that they are taught early—and forcibly—to be satisfied by a drink of water if no one is available to breastfeed. It is specifically to make her infant more attractive to caretakers that a mother beautifies her baby with painted symbols, for “if a baby is irresistibly beautiful, someone will be eager to carry the little one for a few hours, and the mother can get her work done.”35 Cultural practices may be infinitely variable, and many customs do definitely take on lives of their own, spinning off idiosyncratic elaborations. But mothers in the genus Homo still need a lot of help with their children. Even though villages idiosyncratically vary, it is still going to take one.

  One of the reasons that Beng mothers decorate their babies with eyebrow pencil, bright orange cola nut paste, and green-tinted growth lines is to make them more attractive to allomothers, a sort of culturally applied flamboyant natal coat. (Alma Gottlieb)

  PROMISING CANDIDATES FOR SHARED CARE

  Primate babies are all born altricial, meaning that they need a lot of care in order to survive, and they are magnetically attractive to at least some other group members. To top it off, some primate mothers can be extraordinarily nonchalant about whether the babies they care for are their own. Their lack of discernment has led some fieldworkers to question whether primates are even capable of distinguishing their own new infants from those of others—although in humans, at least, there is evidence that they can. Still, consider the remarkably undiscriminating mothers described in a recent issue of the journal Primates.

  Researchers studying northern muriqui monkeys in the forests of Minas Gerais in Brazil watched as two multiparous, experienced mothers descended from the trees to drink. Each held a new infant, one a male born eight days before, the other a four-day-old female. Somehow, in the course of thei
r terrestrial excursion, the mother of the younger baby ended up carrying—and suckling—both babies, one on each teat. Not until some 36 hours later did the mother of the older infant manage to retrieve a baby, but she retrieved the wrong one—the younger female rather than her own son. The swapped infants were subsequently raised to independence by their respective foster mothers. Had the infants in question not been different sexes, known to the researchers from birth, it is possible they would never have detected the mismatch. Apparently neither mother did.36

  Although the circumstances were unusually well observed, the muriqui mismatch was by no means an isolated incident. On rare occasions when wild cebus monkeys have happened upon orphaned infants, females have picked them up. A wild spider monkey once picked up a howler monkey infant abandoned in the forest for unknown reasons.37 Monkey mothers who have lost their own infants sometimes steal and then adopt the infant of another female. Even the most seemingly aloof chimpanzee male will adopt and successfully rear an orphaned sibling (provided the infant is close enough to weaning age). They remind me of the seemingly misanthropic old hermit Silas Marner, who finds himself mesmerized by the abandoned toddler Eppie’s golden hair. Thus does the appeal of babies override ordinary powers of discrimination.

  Unquestionably, the raw material for misdirected parental care, and with it the potential for the evolution of shared care and even cooperative breeding, is present among monkeys and apes. Like the warblers and other birds whose nests are routinely parasitized by cuckoos, primates find all infants attractive, including infants not their own. Aware of how easily monkeys and apes accept new babies, professionals managing primates in captivity frequently recommend cross-fostering (removing a mother’s baby and substituting another) as a discord-free technique for introducing new “blood” into a breeding colony to keep it from becoming too inbred. Were the keeper to release a strange adult into the troop, he or she might be attacked and yet would be unable to flee or to skulk on the outskirts, until becoming accepted by others in the group, as occurs in the wild. By introducing strangers as infants, keepers ensure that the new group member will be immediately accepted, picked up, carried, and introduced around by a local female, and therefore accepted by the adult male as well, avoiding much potential mayhem.

  Having learned about this unabashed readiness of mothers to accept substitute babies from the colony managers, researchers now use cross-fostering as a tool in behavioral experiments, placing an infant from one species with a mother of another and observing outcomes. This has become a research method of choice to tease apart “nature” and “nurture” and to study the interaction between genetic instructions and rearing environments.

  Innate primate responsiveness to infants plays out similarly among humans. People readily accept and bond with adopted babies, especially infants shortly after birth.38 Roughly 120,000 legal adoptions take place every year in the United States. Foster-care situations total four to five times that number.39 Per capita, adoptions are probably even more common in traditional societies, although in those cases adopted children are often relatives, and nepotism looms large.40 Adoptees may be orphans, overstock, or children fostered in from families willing to loan or let them go altogether, in the hopes that their children will encounter better prospects or because they are too great a burden at home.

  As in other cooperative breeders, many of these fostered young help out, “paying to stay.” They are not necessarily well-treated. There is no longer any doubt that—primatewide—infants are at risk of being killed by unrelated members of their same species, and that in humans foster children and stepchildren run a significantly higher risk of discrimination, exploitation, and abuse.41 Years ago, I had trouble convincing colleagues that this was so. Today the pendulum has swung the other way, so that genetic relatedness is too simplistically and dogmatically invoked, leading evolutionists to overlook powerful human urges to look out for children. As in other animals, genetic relatedness and self-interest are not the only explanations for “the kindness of strangers.” A lot depends on circumstances, on the individuals involved, on their past histories, and on where and how babies are encountered, as we saw in Chapter 5.

  An innate attraction to babies is a highly conserved primate trait present in most monkeys and apes. The neural mechanisms for neonatal attraction were almost certainly present in the common ancestors of Great Apes and humans, especially in females. Timing and the particular circumstances under which adopters and stepparents are exposed to infant cues will have important effects on how they subsequently treat unrelated infants. Like all primates, humans can be magnetically attracted to infants, and some people adopt babies simply because, to use a phrase adoptive parents frequently use, they “fall in love” with them.

  The general responsiveness to infant signals so typical of primates highlights what promising candidates for the evolution of shared care apes would be. Not only can we take for granted that the neural mechanisms and underlying endocrinology for responding to needy immatures were already in place, but other circumstances as well would have favored shared care. Like many other primates, the African Great Apes are highly social and are also characterized by relatively slow life histories. Paleontological evidence as well as comparative behavior from extant ape species indicate that our ancestors lived year-round in highly gregarious, mixed-age communities with slow-maturing young. Babies would have been born excruciatingly helpless, taking years to grow up. Membership in a group would have been essential for mothers to rear young, and groupmates would have been chronically exposed to cues emanating from babies.

  We also know that all African apes passed through the late Pliocene-Pleistocene crucible of unpredictable climate change with recurring periods of food shortage, the sort of conditions that might force mothers to seek provisioning help from others. These are precisely the sort of conditions that in other animals promoted shared care, if not the evolution of full-fledged cooperative breeding. Yet even though shared care—and, in the case of callitrichids, cooperative breeding—did evolve in many other species of nonhuman primates, none of the Great Apes living under natural conditions in the wild exhibits shared care. Why not?

  And so, once again, we come back to the same question. In Chapter 1 I pointed out that mind reading and the quest for intersubjective engagement were far more developed in humans than in other apes. In Chapter 2 I asked why our ancestors evolved in this direction, while other apes never did, even though they would have presumably benefited as much or more from enhanced social learning or in-group cooperation. In Chapters 3 and 5 I showed that allomaternal care in the form of provisioning would have been essential to infant and child survival among ancestral humans, and I explained how such shared care produced developmental contexts where infants who paid more attention to both mothers and others would benefit from correctly gauging their intentions and engaging their solicitude. The children good at doing so were both more likely to survive and also cognitively and emotionally transformed.

  In Chapter 4 I explained how shared care and provisioning was conducive to the development of infants’ capacities for monitoring both mothers and others. Such increased attention to their feelings and intentions was accompanied by Darwinian selection favoring survival of youngsters who excelled at mind reading, so that, through time, intersubjective engagement became increasingly important in the genus Homo. In Chapter 6 I took readers on a comparative excursion of cooperative breeding outside the order Primates and summarized the most important explanatory theories for why alloparents would ever be willing to care for the young of others. I discussed how cooperative breeding evolves in the first place and how it is maintained. Finally, in this chapter, I returned specifically to the primate case, stressing how responsive primates are to infants and how preadapted they are for the evolution of shared care.

  If shared care really was a crucial precondition for the evolution of intersubjectivity, and if all primates are to some extent preadapted to evolve it, the absence of shared
care in other apes brings us back to the initial question: Why us and not them? We may have explained why our ancestors embarked on an evolutionary path that left them more sensitive to the mental states, feelings, and intentions of others (because they started out as cooperative breeders), but we have not explained why only this line of apes adopted this mode of infant care and childrearing in the first place. After all, other apes are also extremely clever social strategists. The more we learn about chimpanzees, for example, especially “enculturated” chimpanzees with exposure to human alloparents, the clearer it becomes that they have at least rough ideas about what others know and intend. Furthermore, given how competitive life is at least in groups of common chimpanzees, presumably their ancestors as well would have benefited from traits that enhanced in-group cooperation.

  All this only increases the mystery: What are the missing ingredients that encouraged or permitted one line of apes to evolve this profound reliance on allomaternal caregivers while other apes stuck with exclusively maternal care? In the next chapter I propose a twofold answer having to do with just who was available to help, and the sort of help that was on offer under conditions where allomothers were needed not just to care for but also to help provision children.

  8

  GRANDMOTHERS AMONG OTHERS