Staring at that skull, I was struck by the fact that this ancient child was somebody's baby long ago. Perhaps she was sick, or maybe he e was accident-prone, or perhaps this baby was some predator's dinner. Standing there, I could picture him or her long ago, I, smiling, laughing, and reaching out to grab a mother's breast. It was the most beautiful thing I had ever seen.

From a biological point of view, the Taung child represents a specific stage of development for Australopithecines, our ancestors that lived from four to two million years ago. Paleontologists tend to concentrate on adults of any species because adulthood is the mature end product; but fossilized babies and children also give clues to anatomy and physiology, to rates of development and growth. Children are not just miniature versions of adults. There are sound evolutionary reasons why infants and children look and behave the way they do—childhood is a specifically evolved stage in the life course. The Taung child emphasizes the fact that we are not born as adults but go through a lengthy period of growth and change. In this child, and all children, are some of the most important secrets of our anatomy and behavior. There are reasons why mice are born blind and human babies cannot hold their heads up. Natural selection has opted for fawns to stand on their own soon after birth, for human infants to smile automatically, and for baby chimpanzees to cling to their mothers' fur. And all of this makes some sort of natural biological sense. The pattern of birth, infancy, and childhood in any species follows a particular course that eventually outlines adult biology and behavior.

Not all babies are the same. Human babies are rather helpless, interested mostly in food, sleeping, eating, defecating, and comfort. Compare human babies with newborn deer. When fawns are born, they immediately stand up and soon are able to run away from danger. Scientists call these two types of babies in the animal kingdom altricial and precocial. Altricial infants are born helpless, usually after a short gestation or pregnancy, and their brains tend to be not quite finished. Precocial babies usually spend more time in the womb, are more alert at birth with eyes open and a brain able to control their limbs and make them move appropriately; their central nervous systems are more advanced, compared with those of altricial infants. Altricial infants tend to be small-bodied, small-brained, and fast-breeding—^such as mice. Precocial infants tend to be largebodied, big-brained, and slow-breeding—^such as gorillas.

Both are reasonable alternative paths to survival; the altricial baby tends to grow faster after birth, whereas the precocial baby has gone through more of its development while still inside the womb. The size of die brain of typical precocial babies at birth, for example, is 4.5 times bigger than the brain of typical altricial infants of the same body weight. But the difference disappears later in life. The altricial brain grows to 7.5 times its size from birth, whereas the precocial brain grows only 2.5 times; in other words, the smaller brain grows almost three times as fast once it is out of the womb.^ This overall physical and ecological framework is necessary to put our own species into perspective. What dictates a strategy for a precocial or an altricial infant, and why did the human path lead to dependent babies? There are, of course, good biological reasons why our fetuses are born at a certain average time and at a particular size.

[...]

These three birthing strategies—altricial, precocial, and secondary altricial—are all related to a complex of constraints and adaptations that molds one species or another. Ecologists see these strategies as a contin¬ uum. At one end are the species that produce a large number of offspring at a rapid rate while investing little in each infant, such as insects (these are called r-sekcud species). At the other end of the continuum are species that reproduce only occasionally and invest heavily in each infant (called Kselected species).^ Mice, for example, have done best by producing large litters of altricial infants that stay in a nest until they develop. I For most imgulates, the horned and hoofed animals, evolution has opted for large animals with alert, fast precocial babies. And the human line is defined by big-brained babies that come out unfinished. There is no easy answer as to why one path is taken rather than another. Sometimes chance may nudge a species in a certain direction. More often, the pattern can be explained as an adaptation to a particular set of environmental circumstances that favor this or that physical change. So far, we only know that the evolutionary history of humans has moved toward favoring big brains, which in turn necessitated developmental and physiological consequences at birth and during infancy.

In 1896, inventor Martin Cooney designed the incubator, a device veloped to aid premature babies. Cooney was the first to advocate separation of infants from their mothers as a medical procedure for the health of the child. In a bizarre combination of medicine and sideshow. Cooney gathered hundreds of premature babies (they were easy to obtain because doctors assumed premature infants would die), put them into incubators, and exhibited them at various expositions and fairs in Amer¬ ica and Europe."*^ Babies were returned when they reached five pounds. But until then, their mothers were kept away. (Cooney would not allow mothers to visit with their infants, but did give them free passes to the exposition.) A photograph of Cooney's exhibit in San Francisco in 1915 shows a brick building with the tide "Infant Incubators with Living Infants" emblazoned across the facade. Inside the exhibit were rows of tiny metal cabinets looking like microwave ovens with wrapped babies inside. It looks modern for the times, hygienic and sterile, but the mothers are nowhere in sight.

Once settled on Coney Island, Cooney saved more than five thousand premature infants over the next few decades; and to offset the cost of their care, he continued to exhibit the babies up through the 1940s New York World's Fair. Cooney's technique was so successful that it was widely adapted by hospitals across the nation when they built premature infant wards. More broadly, it became standard practice even for normal babies—^it was considered healthier for even these babies to be taken away and placed in incubators where they would be observed by nurses, rather than to be left with their mothers.

In all human cultures there is some sort of father in the typical family, either the biological father or a male maternal relative, who acts in ways that all societies would agree are paternal.^ ^ Anthropologists suggest that biological fathers in particidar have an important parenting role in societies where family life is strong, women contribute to subsistence, the family is an integrated unit of parents and offspring working for the same goal, and men are not preoccupied with being warriors These fathers must be assured of true paternity if they are going to invest in children; thus all societies have many mechanisms, such as legally sanctioned monogamous marriage and heavy punishment for adulterous wives, to reassure fathers that the children of the household are theirs. Although the degree of fathering across cultures varies, the potential for human males to contribute to infant care is great. They can provide food. shelter, protection, and daily care, and they usually do. There is also evidence that males can be intimately connected to their children, and that they have been selected by evolution to be good fathers.

s any new mother or father knows, nothing so invites advice as a new baby in the house. Other parents. Grandma, the lady next door, a stranger on the street, the family physician, and stacks and stacks of child-care books are happy to give directions about the "correct" way to care for an infant. What most parents do not know is that these various tidbits of advice, and even the consensus "rules" of parenting that have such an aura of credibility, are, for the most part, based on a mix of tradition, fad, and folk wisdom with a modicum of science. In fact, few have ever studied whether or not the rules of one society work better than the traditions of another society in producing functional, happy adults. If a parent talks to his baby, will it learn to speak earlier? No one knows. If you sleep with your baby, will it become emotionally dependent? Who knows. Yet societies establish these "rules" about various parenting techniques that imply there is a right and a wrong way to go about parenting. And the advice is usually offered in such ominous tones—^make a mistake and your child may turn out socially inept, not very bright, maladjusted, or worse—that parents often follow these rules, or accept die advice, without considering that there might be alternative ways that also make sense. In addition, even the hard-and-fast parenting rules slip and slide, evolve and change, as societies change.

;ct. What parents want even influences the very ways they label children. Sara Harkness and Charles Super found that when parents in three cultures were asked about intelligence, their views of what constitutes a smart child differed.^^ In America, an "intelligent" child is one who is aggressive and competitive; in Holland, die intelligent child is one who is persistent, strong-willed, and demonstrates a clarity of purpose; for the Kipsigis Africans, the most intelligent child is the responsible one who does his or her chores.^^ Each household tries to provide a setting that is believed to foster the culture's particular brand of intelligence. Americans use all kinds of visual and verbal stimuli to catch the baby's attention and encourage it to interact. We line the crib with black-and-white signs to stimulate vision; we converse for hours in one-on-one lessons, convinced that this verbal interaction will improve cognitive abilities. Americans try to instill self-esteem in their children; self-esteem is a word not easily translated into other languages because the trait is not part of the cultural milieu of other groups—it is of import only in a competitive self-achieving society. The Dutch, in contrast, believe that regularity, rest, and cleanliness promote intelligent development, so much so that when children throw tantrums, as they do all over the world, parents assume there has been a break in the child's routine that has caused the episode. And Kipsigis parents load their children with chores. Beginning at two years old, an age at which Americans would call them toddlers, Kipsigis children are given household tasks. By the time they are six years old, these kids typically spend half of their time working for the family. People from each culture would be incapable of raising their children any other way. Imagine an American child doing househohold chores at two, with little playtime. We would mourn die loss of "childhood," that carefree time of exploration and development. In the same way, a Kipsigis mother would be horrified to see irresponsible, lazy American children with nothing to do but play games. How could that at child, she might comment, grow up with any brains at all? The point is t that we all agree in a general sense on what intelligence is, and we all agree that to be intelligent is better than being stupid, but each culture emphasizes and appreciates different aspects of intelligence.

As the pop pundits keep reminding us, we are becoming a global culture. We share the same TV shows and movies, drink the same Coca-Cola, and shoot the same Kodak film. But this "global culture" is highly superficial—^it is only the gloss of popular culture, apparent only in what people over the world would like to buy. I am guessing that those boasting of an electronic superhighway where "anybody" can be connected to "anybody" have not traveled much in the third world; they are blinded by the affluent economy of their own culture into thinking they share much of anything with a Malaysian forester or Sudanese refugee. More illustrative is the fact that one out of every five women on the planet is Chinese, and that most of the people in the world have never spoken on a telephone. We do not share the same culture or the same economy, and it will be a long time before we do, if ever.

Anthropologist John Whiting found a simple association between climate and parent-child co-sleeping (among other behaviors).^ Evaluating 136 societies for which he had information. Whiting outlined four kinds of typical sleeping arrangements for a household: mother and father in the same bed with baby in another bed; mother and baby together and father somewhere else; all members of the family in separate beds; and all members of the family together in one bed. The most prominent pattern across cultures, Whiting discovered, was mother with child and father in another place (50 percent of the 136 cultures). In another 16 percent, the baby slept with both mother and father. Many of these cultures, he wrote, were polygynous, so that fathers were moving among households and beds, and the stable unit was actually each mother with her children. Whiting also found a connection to cold weather. Men and women, that is, couples, routinely sleep together in places where the winter temperature falls below 50 degrees—presumably for warmth more than any other reason—but they often have separate sleeping arrangements where the climate is warmer. The sleeping place of babies, on the other hand, usually conforms to a different climatic situation—they "usually" stay with mother in areas with warm climates, but in colder climates, they are swaddled in blankets and strapped to cradleboards to minimize heat loss. These cultures, however, represent a small minority of the human population.

The fear of overlaying haunts many parents in Western culture today. Most believe it is possible to roll over and squish a baby or suffocate it under a mound of blankets. But as infant sleep researcher McKenna notes, babies are born with strong survival reflexes, and they will kick and scream before they let anything clog their airways. The simple evidence that most babies around the world today sleep with a parent and they are not dying from suffocation should be enough to convince parents that it's pretty difficult to roll over on a baby and not notice. True, soft mattresses and plush pillows represent a very real risk of suffocation; also, if the baby is wrapped so tightly it can't express its natural instincts to push something away, there could be a problem. But Western parents who fear they will suffocate babies are wrong. In a healthy atmosphere, where parents are not intoxicated, on drugs, or obese, the chance of killing an infant by overlaying is zero. If this is true, why does the myth persist? The myth of overlaying persists because in many Western cultures there are also social, emotional, and political reasons to keep babies out of the parental bed. In the seventeenth century, the Catholic Church became concerned with the possible sexual vulnerability of young girls sleeping with their fathers. At the same time, European culture was developing notions of romantic love and redefining marriage as a conjugal bond rather than an economic or political unit. Suddenly the mother—father relationship took on a separateness within the larger idea of family. When the relationship of mother and father became a sacred, private, sexually intimate bond, parental privacy was born. Children, although offshoots of the bond, were not allowed to interfere with the spousal union. Infants and children, on one level, were seen as a threat to that bond and to the patriarchy that established the father as die family authority. This view later led to the Oedipus complex in Freudian psychology—a drama that cannot be played out unless it is understood that mother and father have a special, private bond in the first place.

Crying is the earliest and most compelling of infant signals," writes Ronald Barr, and surely there is no sound on earth more piercing than the cry of an infant. The ability to cry was hard-wired into human babies long ago as a potent signal to get adult attention. Like other primates, human infants needed to be able to send a message of distress to motivate action on the part of someone more able. The same kind of vocal signals are found in Rhesus monkeys, for example, which have very distinguishable distress noises called "coos." During a coo, the lips protrude into an "oh" and produce a plaintive series of cries when the infant is separated from its mother. Monkey and ape babies also shriek and scream and produce a deep-throated geek noise, all as signals to others. These signals, of course, have evolved in primates and other animals because they work; the sounds bring the mother closer. Animal babies call when something threatens or frightens them, thereby making it known that, from the infant's point of view, something is terribly wrong. For humans, nothing compels a parent to do something more quickly than a child's piercing wail. And that's why crying is, in Ronald Barr's nomenclature, a paradox. It is a signal that evolved to broadcast an infant's unhappiness and motivate a parent to address the cause of its distress. But that same signal can, very easily, send parents over the edge. For example, reports of child abuse and child homicide often contain comments about a parent's or caretaker's ultimate frustration with a crying infant, and their claims that they just couldn't take it anymore. And so what evolved as an adaptive signal can be destructive under certain circumstances, which doesn't make evolutionary sense at all.

Crying evolved to serve the infant's purposes: to assure protection, adequate feeding, and nurturing for an organism that cannot care for itself. By definition, crying is designed to elicit a response, to activate emotions, to play on the empathy of another. The "other" is usually the mother or father or a related caretaker. The caretaker has also evolved the sensory mechanism to recognize that infant cries are a signal of unhappiness, and thus be motivated to do something about it.

This kind of symbiotic relationship certainly made sense in the EEA. Even back then we were a large-brained species whose infants had to be born early in their physical development because of the constraints of the bipedal pelvis. As a result, human babies could not yet talk and thus had to communicate by other means. In the EEA, crying probably promoted survival because it kept the mother close, resulted in the infant's being fed as she held out the breast to quiet it, and kept parents attentive against predators. A quick cry, then, made evolutionary sense, at least in the EEA. At the most fundamental level, crying is an adaptive strategy because it keeps a baby alive and well fed and therefore ultimately passes on genes and improves a parent's reproductive success.

It might also have an added evolutionary advantage. When a baby is allowed to feed continuously, ovulation in the mother and conception of the next sibling who will take over breast-feeding is delayed. And so the combination of crying and the continuous feeding that results from crying is also an effective adaptive strategy on the part of the infant; infants who evolved with these traits had a better chance of survival than those who did not. In this scenario, the infant is not simply a helpless or passive recipient of parental largess, but an active initiator of a synergistic relationship with the parent.

In some cultures today, the fit between infant cries and survival has been altered and crying has become, as in the case of colic, a maladaptive trait that no longer promotes survival. Any trait can become maladaptive when the environment changes; what once was "good" now becomes neutral or "bad" because it is no longer effective under the new conditions. When crying is continual and annoying to the point of placing the infant in danger of abuse or neglect, it is a clearly maladaptive signal. And that may be what has happened in our modern age. It is not that babies have changed, but rather that the environment in which babies send their signals has been altered.

It might also be difficult to extend the categories of temperament across cultures when the categories mean different things in different environments. For example, "difficult" babies in Western cultures are those who do not sleep for long periods and those who cry. Under a different caretaking package, these reactions would not even show up. More important, there is no reason to assume that what is "bad" in one culture will end up "bad" in another culture. Dutch researcher Marten de Vries followed a set of Masai infants in Kenya during a period of great drought in die I970s7^ He labeled babies "difficult" or "easy" based on his observation and the application of Western categories of adaptability, intense reactions, regularity, and whether or not they were manageable. He also used the standard Western Infant Temperament Questionnaire, modified for the Masai (he had to delete questions about going to the doctor and add questions about being carried), to ask parents how they perceived their babies. He wanted to categorize the babies on a continuum of temperament, and so he concentrated on the ten easiest and ten most difficult babies as his subjects. Returning three months later, he sought out the parents of the twenty babies at the extremes but found the parents of only thirteen—Masai are, after all, nomadic people. The parents had been dealing for years with the destruction that a drought causes to people who make their living off the land, and all the babies were already malnourished. In the following three months, during some of the worst of the drought, seven of the thirteen infants he had located died. But interestingly, only one of the so-called difficult babies, as categorized by Western criteria, were dead, while six of those he labeled as easy were dead. De Vries surmised that traits we perceive as difficult under ample conditions might be more beneficial to survival during times of nutritional stress. A "bad" temperament might be evolutionarily advantageous under certain circumstances or in certain environments. In times of nutritional deprivation, it may be the fretful baby that gets the most milk, or is picked up most often. It is only in our affluence that we use the negative word "difficult" to describe the fact that the baby is evolutionarily designed to gain attention. The perceptions of temperament, in other words, are relative.

About sixty-five million years ago, at the end of the Mesozoic era and the beginning of the Cenozoic, the niche once dominated by the dinosaurs was available for other creatures. The opportunistic could move into that niche now empty of large reptiles, and prosper in their place. Among these creatures that flourished were small egg-laying animals. group that had been around for at least a million years and that sported specialized patches on their chests. Sitting on their eggs, the mothers of these species gave off body heat through these warming pads. The patches also had a glandular function, secreting a liquid rich in lysozyme that coated the eggs with an antibacterial slime and destroyed harmful microorganisms. When the eggs hatched, the new infants probably licked up some of that egg-coating ooze, which turned out to be immunologically protective once ingested. It may be that the newly hatched babies were simply hydrating themselves by licking their mothers' chests for the liquid that had collected there.^ In any case, those babies who licked up the fluid gained an advantage for their efforts in terms of survival—^they either grew faster or bigger, or they were healthier than those who ignored the opportunity. Maternal ooze eventually evolved strong nutrient properties that could sustain a baby even when the mother was unable to bring back food to the nest or the infant was too weak to forage on its own. Thus lactation was born.

At first the mammary gland must have been a kind of sweat gland, an eccrine gland, a gland that excreted material to the outside of the body like those found in armpits that excrete water and electrolytes. In fact. die gland might have emitted distinctive and attractive odors that brought premammallian infants close to their mothers' chests. Eventually these chest glands changed into apocrine glands, tissue that can synthesize proteins, carbohydrates, and lipids rather than just excrete water. We know that breasts, and the liquid they manufacture, must have coevolved with the infants' ability to find the nipple, suck, and digest what was ingested. Mothers must have already been adapted to stay close to their infants and engage in some sort of positive maternal care, and ifants must have been selected to turn only to their mothers and what they offered. Eventually these premammals began to give birth to live young, and most of them developed hair. But their most distinguishing characteristic, what set them apart from reptiles and birds, was their ability to lactate from specialized glands to nourish their young. Thus began the evolutionary path of modern mammals, animals in which the female members invest highly in each offspring by manufacturing and secreting for days, weeks, or months a fluid that is the sole food of their young.

Our notions of mother's milk come from what we see, and for most of us the milk we see is cow's milk, a brilliant white liquid. But milk from other species looks quite different—kangaroo milk, for example, is pink. But whatever the hue, breast milk is species-specific; that is, the composition is finely tuned to the particular growth and maturational needs and digestive system of the young of each species.^ ^ For example, cow's milk is higher in volatile fatty acids than human milk, and humans do not digest volatile fatty acid that well. So while cow's milk is easy for baby cows to digest, it causes intestinal gas in human babies. Cow's milk is also higher in iron than human milk, but the iron is a type that is not easily absorbed by the human digestive system. Because of this, human babies absorb more iron when they drink human breast milk than they do when they drink cow's milk, even though cow's milk contains comparatively more iron to begin with. Species-compatible milk is also easier to digest; it takes human infants twenty minutes to digest breast milk, and four hours to digest formula milk made from cow's milk. Human milk also contains about one hundred amino acids, vitamins, and minerals, including salts and sugars, in a recipe made specifically for the needs of human infants.

Milk composition also offers clues to the intensity and style of species-specific maternal behavior. In species where mothers are expected to feed only occasionally and leave babies in a nest for long periods, the milk is high in fat and protein so that infants can be both nutritionally compensated (by protein) and satisfied (with fat) for long periods alone. When the milk is low in fat and protein, as it is in humans, it is an indication that breast-feeding is designated or intended to be more continuous.^^ Human milk is 88 percent water and 4.5 percent fat on average, depending on the style of feeding; interval feeding with long spaces in between produces lower-fat milk, while continuous feeding produces higher-fat milk. In contrast, for example, seal milk is made up of 54 percent fat, which is an extremely high fat content. Predictably, baby seals feed in long intervals; they also need high fat to grow thick layers of body fat to keep warm in a cold aquatic environment.

More significantly, the breast—bottle controversy has moved far away from the question of what is best for babies. The decision for substitute milk is influenced by the pressures of corporations, their advertising, and their lobbies. The money game behind the production of formula has overpowered what might be best for babies here in first-world countries and for babies more at risk in third-world countries. It takes about $1,800 a year to feed an infant some kind of powdered or canned formula. In third-world cultures, and for the working poor in developed nations, the cost is crippling. It is also undefendable given that a free alternative is readily at hand. Where medical care and hygiene are poor, many babies fed on formula become sick and die. Some researchers claim that bottle-feeding in underdeveloped countries increases the risk of infant mortality tenfold. And UNICEF estimates that 1.5 million babies die each year because they are not breast-fed. Loss of natural immunities and the lack of adequate sanitation provide an environment in which formula-feeding is not the safest alternative for infants, and thus infant mortality increases. In the West, where conditions are better and fewer babies die directly from formula-feeding, many more are sick with chronic health conditions. The U.S. National Institute of Environmental Health and Safety estimates that four out of every thousand infants in the United States die because they are not breast-fed. The increase in respiratory and gastrointestinal disease, the greater number of inner ear infections, the additional allergy shots necessary, and the extra pregnancies and births that come from the loss of the contraceptive effect of lactation, all combine to increase health costs shared by all.

Interestingly, the third world seems to be more savvy about how corporations push formulas on expectant mothers. The dramatic rise in mortality among formula-fed babies in developing nations has induced some professionals to initiate changes to combat the invasion of Western infant-feeding practices. For example, in Papua New Guinea, a prescription is now needed to buy a baby bottle. In the Philippines, hospitals now forbid formula-feeding and promote breast-feeding. As a result, fewer staff have been needed to prepare bottles and less electricity has been used to sterilize equipment. The hospitals estimated they saved over $10,000 in one year from their new program. Most important, there have been rapid decreases in infant illness. Other hospitals around the world, such as one in Quito, Ecuador, have copied the Philippine initiative.

Even when women do decide to breast-feed, they sometimes feel they are thwarted by their own bodies. "Insufficient milk" is cited as a major reason women in the West terminate breast-feeding after a few days or weeks. The syndrome is fascinating because it is a clear example of a disease being "invented," defined, and then perpetuated by culture at large. In only about 5 percent of the cases is there something making it physically impossible for a woman to breast-feed. Before bottle-feeding came into vogue, women rarely, if ever, reported a lack of milk. But when breast-feeding went out of fashion in the 1940s, this new syndrome appeared. The real cause of insufficient-milk syndrome appears to be a confluence of social changes—hospitals took over the birth process and separated newborns from their mothers, doctors recommended interval feeding, and artificial formula presented a reasonable alternative. It is interesting to note that insufficient-milk syndrome appears only in Western industrial nations and has yet to be found in other cultures. Why do so many women in affluent countries say they have no milk for their babies?

A more flexible construct of normality also has practical applications. As all parents in Western culture know, there is a "normal growth curve" against which all infants are compared when they are brought in for visits to the pediatrician. This standard is used to evaluate babies' growth, and if die baby falls drastically below die curve, pediatricians recommend intervention. But pediatrician Glen Flores, who codirects the Pediatric Latino Clinic at the Boston University School of Medicine, points out that comparing Latino babies to that "normal" curve is a mistake. That initial and now widely accepted curve was developed based on a group of white bottle-fed babies from Yellow Spring, Ohio, during the I950s.^ This information is important not only because white babies are born heavier, but bottle-fed infants also grow faster and fatter than breast-fed infants, regardless of their ethnicity. In this particular case. Latino babies in America are also born smaller and therefore follow a slower growthrate curve. The curve, then, in reality is "normal" only for other white bottle-fed infants. Using that curve to evaluate Latino babies may cause pediatricians to intervene in unnecessary and inappropriate ways. And how disturbing it must be for Latino parents to be shown that curve and made to feel that their baby is not healthy. What is needed, points out Flores, is more data on birth weights, growth curves and such from various ethnic populations—that is, a widening of the concept of the normal growth curve.

Obtaining a more broadly informed view of parenting means examining parenting styles not just cross-culturally but through evolutionary history as well. Underneath the cultural twists that skew our behavior lies a natural biology, a human nature, that evolved a certain way for good biological reasons. Organic beings are, of course, subject to natural selection, and the path of evolution is not a perfect path. Contrary to popular belief, evolution does not select away all the defects and save only the perfect models. Instead, natural selection navigates a trade-off between cost and benefit; it deals with existing constraints and checks out the options, and then ends up with a compromise. Every species, every organism, is a compromise. As anthropologist Carol Worthman puts it, "Biological systems are Rube Goldberg systems. They don't always work perfectly but they work well enough." Apply that evolutionary frame¬ work to the evolved parent-infant dyad, and the same kind of Rube Goldberg solution appears. The human baby has a big head and has to be born too soon, so it is more dependent than the babies of other mammals. As a result, all kinds of mechanisms kick in to attach parents and infant in a physiological and emotional dyad. It's a patched-together sort of system, with strange bells and odd little whistles, and it often breaks down; but for the most part, it does work and babies grow up healthy.

The evolutionary perspective can be both comforting and disquieting. The best thing that evolution gives us is the flexibility to deal with all the various pathways to the same end result—a healthy, successful offspring that will grow to reproductive age and pass on more genes. "If evolution was going to design an adaptive organism," says Ronald Barr, "it would design one with multiple pathways."

Archaeologists have discovered that since the Pleistocene, humans lave always suckled infants for several years. Using biochemical analysis given human population when its children moved from breast milk to other foods. In one group of skeletons from South Dakota dated between 5500-2000 b.c., children were apparently depending on food other than mother's milk by the time they were twenty months of age.^' Recorded history also tells a similar story. Middle Eastern groups in 3000 B.C. were breast-fed for two to three years, which was the common age of weaning for Hebrew populations. At another North American site near the Missouri River dated to the seventeenth century, researchers were able to determine that infants were breast-fed exclusively for one year and that weaning was between two and six years of age. This work has been confirmed at other sites, where researchers have also found evidence that not so long ago there typically was no abrupt change from breast milk to other foods, as we often think weaning should be, but a gradual change.^ ^

In all cases, this hominid blueprint of the way babies were fed for 99 percent of human history indicates breast milk as the primary or sole Food until two years of age or so, and nursing commonly continuing for several more years.

From an evolutionary point of view, it would seem that last-feeding should be one of the more instinctual behaviors, like eating or sleeping or sex. In most mammals, if mothers don't know how to offer their milk or babies don't know how to suckle, the infant dies. If die purpose of reproduction is to pass on genes, it would seem that feeding would be one of the more hard-wired biological behaviors. In explanation, Wiessinger offered this story: A female gorilla, born and raised in a zoo, gave birth to an infant. In an attempt to nurse it, the mother held her infant incorrectly, with the back of the baby's head toward the nipple. The keepers feared for the infant's life and took the baby away. During the gorilla's next pregnancy, the keepers tried an ^ experiment. They lined up a group of breast-feeding humans outside the cage and allowed the mother gorilla to observe. When her next infant was born, the mother gorilla, too, turned the baby toward her breast and everything went fine.

The point is that breast-feeding is not necessarily an automatic response for any mammal, especially under less than natural conditions. It requires certain triggers and certain coordination between mother and offspring. And humans are no different from other species. Imagine taking a newborn calf or lamb or piglet away from its mother in order to wash it and do tests. Farmers know that any separation of mother and newborn farm animals results in rejection of the infant by the mother or an inability on die part of the baby to suckle. Although we recognize this situation in livestock, we have only recently become aware that human babies have the same sort of reflexes designed to seal the pact between mother and infant right after birth. As many pediatricians and hospital staff now know, the sucking reflex is strongest within the first thirty minutes after birth. Newborns placed on their mothers' bellies directly after birth also begin wiggling and moving determinedly toward the breast when left on the mother's body for twenty minutes. "But," explains Wiessinger, "if you take the baby away and give him a bath and take his footprints and measure him and wrap him up and bring him jack, he's lost the dance." This interruption in the loop can derail the whole process. In other words, breast-feeding is instinctually and biologically triggered, but it can also be behaviorally disrupted. For example, when the birth process became medicalized in the United States in the 1930s and more babies were born in hospitals, the number of mothers breast-feeding dropped. Also, some mothers were unable to breast-feed successfully. Their failure was, in part, probably due to the long separation of baby from mother for long periods in the hospital right after birth. Today, with birthing rooms and babies kept close to their mothers at all times, breast-feeding has been proceeding more smoothly.

In a more evolutionardy appropriate infant-caretaker scheme, the infant is a social partner, part of a dyad. Both mother and infant are interested in being in equilibrium, that is, in a stable and contented state. This goal is adiieved by mutual regulation, by reciprocity, and by keep¬ ing tabs on each other. This system nicely describes the infant-caretaker pair, and as I have presented in Chapter Two, there is a great deal of evidence that infants and those who love them are attuned to each other and have evolutionarily selected to be so. They are a biological system of interdependence that seeks the same goal—stability. The infant's part in the system is straightforward. It monitors its internal state and then announces any deficiencies, crying for food, warmth, or touch. Crying and smiling are signals of what is right or wrong with the baby's, its equdibrium. And when there is a tilt in the equilibrium, the baby tells the other part of the dyad and seeks reciprocity. The problem comes when die other half of the dyad is not checking in, or is refusing to hold up his or her part of the system; the pact is broken and a mismatch ocoirs. A mismatch, an unanswered signal, is of course not always bad. Think of a tennis game. When one player lobs a ball off to one side of the court, it makes the other player run and reach out, which theoretically pushes the opponent to be a better player in the long run. This view might be applied to the scenario of one type of Western caretaking system—food, touch, and comfort come, but not on an EEA infant-requested schedule. Th( infant-requested schedule. The system is not perfect from the baby's point of view—perhaps a few too many balls are hit out of bounds, and needs are lobbed not when asked—but the interaction does follow some sort of game plan.

What seems to work best is simple human contact. Peter Wolff long ago demonstrated that picking up a baby works better than anything else to stop any baby from crying. In another study, infant researchers BeU and Ainsworth showed in the 1970s, with a sample of twenty-six infants, that consistent and prompt response by the infant's mother is associated with a decrease in the duration of infant crying. Urs Hunziker and Ronald Barr recently took this idea even further when they experimented with different infant carrying schedules to test whether or not carrying could have a proactive effect on crying. They recruited a group of parents with newborns and asked half of them to carry their infants at least three hours per day beyond feeding time. The other subjects were not told to carry their infants any more than they normally would. When the babies were twelve weeks of age, the mothers were asked to bring in diaries in which they had noted when and how long their babies cried, The researchers found that the control mothers carried their babies on average 2.7 hours a day and the mothers involved in the experiment carried their babies about 4.4 hours per day, an increase of only 1.7 hours per day. The diaries show that during the peak crying period at eight weeks of age, both groups of babies cried with the same frequency, but those that had been carried longer cried 43 percent less in duration than those carried a shorter time per day; the frequency of crying was the same but the duration was almost half as much. The infants who were carried more also reached their crying peak on the early side, at four weeks, and leveled off at six weeks. Interestingly, when this same procedure was later tried on babies already labeled as "colicky," it didn't work as well. Even though half of the 66 colicky four-week-olds were carried 56 percent more (2.2 hours longer) than the other colicky babies, they didn't cry less. Perhaps longer carrying would have been effective if it had been done from birth, but either one month of age is perhaps too late for differences in parental style to have much effect on crying or these babies labeled as colicky were just not as susceptible to being comforted in this manner.

Although type of food and total amount of food do not seem to dramatically affect infant crying, the timing of food and the way food is delivered do seem to be of prime importance in staving off crying. Comparing members of the La Leche League, women devoted to relatively continuous breast-feeding, and a group of mothers following die more traditional American pattern of feeding on a schedule with hours between feedings, Barr and his colleagues explored the possibility that the length of time between feedings might have an effect on crying. Observing these two groups at home, and through daily diaries kept by mothers, Barr and Elias found that the quietest infants were those who were fed at short intervals and whose mothers quickly responded to their crying. Interestingly it was the combination of feeding and response, and not just food, that was so effective; the infants of mothers who fed in short intervals but were slow to respond, and of those who fed with long intervals between feedings but responded quickly, all cried a lot. In other words, it's not just the constant availability of milk that makes a baby happy, it is also an engaged mother who responds quickly.

Pediatricians and child experts suggest trying one soothing technique after another. But the best answer, according to this research, is a particular parenting style. What crying babies seem to need most, or what decreases their crying, is a caretaking package that puts their world right. And some babies seem to yell louder than others for a change if their world is not in balance.

when they are more used to sleeping alone, sleep differently when with when they are more used to sleeping alone, sleep differently when with their mothers. The babies seem to spend a greater percentage of their sleep time in levels 1-2 and less time at the deeper levels, exhibit more REM sleep, and are awake longer. In other words, they are more often moving among sleep levels, and they sleep lighter.

Christopher Richard, Mosko, and McKenna have also found that most co-sleeping pairs spend the entire night facing each other. Even if mothers normally put their babies face down on the solitary night, they position the baby on its back or side on the co-sleeping night and instinctively in a position so that mother and baby are en face. Babies seem to know this is what they want; on the co-sleeping night, even if they are on their backs and have a choice of where to look, they move their heads to face the mother. This might, at first, seem like a potentially dangerous situation. Indeed, the researchers have shown that adult women breathe out a hazardous amount of carbon dioxide at close range, especially when a blanket forms a pocket before an adult's face. But an atmosphere of CO2 in the face might also be beneficial for infants because it changes the immediate atmospheric environment for the baby and triggers the for co-sleeping babies. Work with preterm infants has shown that skin-to-skin contact increases infant skin temperature, and since babies have trouble staying warm in cold climates this is an advantage as long as they don't get overheated. Such contact also stabilizes infant heart rate and reduces crying and sleep apneas. If nothing else, co-sleeping clearly makes for a very different external environment than sleeping alone.

p; But the most startling result of McKerma's research can be observed, even by the novice, on the videotapes. No one can miss the fact that cosleeping results in more attention by the mothers. When McKenna scored mothers' co-sleeping behaviors and compared them to what mothers did when they slept in a different room and got up at night to attend the baby, co-sleeping mothers exhibited five times the protective behaviors toward their babies. They repeatedly kissed, touched, and repositioned the baby. They readjusted blankets and comforted the baby when it fretted. And sometimes these mothers, as the polygraph showed, were not even conscious. They reached out and cuddled their offspring instinctively, keeping them from harm's way.

Co-sleeping babies, then, are under constant physical supervision, and are just a whisper, a pat, and molecule of carbon dioxide away from the person who is looking after them. Solitary babies, although fed when they cry and picked up when they whimper, never receive this kind of intimate treatment during the night.

But there is more to the interaction than a matter of adults putting on i a show. When babies and adults interact, they are partners in an interactive social dance in which they jointly regulate each other, and this dance is essential for the baby's social and psychological development Renowned pediatrician T. Berry Brazelton noticed in his practice that babies and mothers seem to follow a typical pattern of play, a synchronized score that moves from attention to nonattention with both partners cueing in on each other's signals. In the lab, babies were offered a fuzzy monkey on a string; and later, when the monkey was removed, mothers were asked to play with their babies. The babies played with the stuffed monkey in a different way than they did with their mothers With the monkey, they focused on it and reached for it, but soon became bored and turned away, never looking at it again. With the mother, the baby engaged with her face, became attentive and excited, and then slowly showed signs of inattention. The mothers all seemed to be highly sensitive to the cycle of attention/nonattention and responded to the "down time" by letting the baby be; and then the cycle started all over again. In experiments where a mother was instructed to act unresponsive to baby movement, the baby repeatedly tried to engage the mother by flapping around and looking at her. When she did not respond, did not take up the baby's initiative toward interaction—looking at each other and paying attention to each other—the baby gave up, looked hopeless, and began self-comforting movements such as sucking on its fingers. As Brazelton points out, with objects the goal is to explore and discover but with people the goal is to engage. And babies happily engage in social play not with some specific goal in mind but simply to establish joint regulation with another human. This is just what one might expect from a human baby, a creature that is adapted to be both an object manipulator, or tool user, and a highly social animal, Child development expert Edward Tronick has pointed out that our most central human adaptation is our communicative competence, and one of a baby's most powerful, most highly adapted, most necessary skills is the ability to exchange on a social level with adults.

In the 1960s a slow revolution in birthing practices began in Western culture. As a result of the influence of John Bowlby's attachment theory and Harry Harlow's infant monkey experiments, the medical establishment realized the importance of physical proximity on the bonding process and babies were not necessarily removed to the nursery. The feminist movement in the 1970s, which helped women assert their wishes, furthered that revolution as it gave female nurses and mothers the support to demand that mother and father be integrated back into the early infant experience. In 1976 two obstetricians, Marshall Klaus and John Kennell, based on their research, theorized that there is a critical early—and limited—period for human mother-infant bonding. They noted a higher incidence of infant abuse and failure-to-thrive children among premature infants; because the infants were premature and had been sequestered in nurseries and away from their mothers, there had been, these doctors suggested, a breakdown of the normal mother—infant bond. They found that although 7 to 8 percent of live infants are born premature, 25 to 41 percent of battered infants were preemies. They surmised that a critical period of attachment had passed by the time the baby was sent home, and that the mother-infant pair consequently lacked the essential positive bond that links them together in a healthy emotional and physical way. Klaus and Kennell also evaluated the various amounts of time that different mothers spent with their newborns and found that those who had had early contact, within the first few minutes to the first two hours after birth, were more attentive in later pediatric exams and showed a few more interactive behaviors with their infants during these exams. Critics pointed out that the tenor of behaviors during an exam a few months later was hardly a reasonable measure of the intensity of the maternal—infant bond."'^ Nonetheless, the Klaus and Kennell work underscored the need to have babies interact immediately with their mothers or to stay with them rather than be taken to a nursery."

By 1978, even the conservative American Medical Association claimed that "bonding" is their official policy regarding mothers and infants, and that fostering the bond is an important component of the birth process. Hospitals now acknowledge that "bonding" does occur early on, and that babies can be medically managed even if they stay with their mothers. As a result, "rooming-in"—where babies and mothers stay together—is now often integrated into the medical model of pregnancy and birth. The idea that mothers, and fathers, must bond with i their newborns as soon as possible after birth is now generally accepted in our culture and sanctioned by the medical authorities. After a p period of about ninety years during which that bond was ignored, dismissed, shattered, and fully re-examined "scientifically," Western culture has now returned to accepting that babies and mothers are a natural pair.

Evidence that there is some sort of heightened awareness by mothers, caused either by biology or emotions, is seen in a mother's ability soon after birth to recognize her infant by smell and voice alone. In several studies, mothers who had spent only a few hours with their newborns were able to smell out their babies when comparing their shirts with the shirts worn by other babies. Mothers are also pretty good at hearing their infants. Women with new infants in wards usually sleep through the cries of other infants but wake up immediately upon hearing their own babies' cries. New mothers are also good at picking out the recorded cries of their own infants, sounds that are spectrographically as individualized as fingerprints. They can also correctly identify the type of cry. be it hunger or wet diapers, when recorded under varying circumstances and played back.

Although this evidence points to an innate maternal instinct for identifying and interacting with infants, it is not a fixed interaction. In fact, all these studies show that with time, mothers get better at smelling and hearing their infants, and that mothers with previous children are better at it than first-time mothers. Although women might come equipped with some of these abilities, their accuracy and skill at using them is improved with experience and learning; this would be expected in a species such as ours, in which learning plays such a major role in behavioral patterns. Even maternal attitude—a positive attitude toward children and one's own baby, which should be the most primate maternal response—changes with experience. In one study, 68 women were interviewed three times: when they were pregnant, three days after birth, and when their children were over a year old. These mothers expressed a definite increase in positive attitude toward their babies—^with time, they became more and more attached.

The real obstetrical dilemma came long after Lucy and her colleagues became extinct, when there was a sudden upsurge in brain expansion. About 1.5 million years ago, die adult hominid brain went from the Australopithecine size of 400 cubic centimeters to 750 cubic centimeters in a species called Homo habilis, the first member of our genus. In other words, the brain just about doubled in size. A mere million years later. the hominid brain doubled once again until it reached its present average size of 1200 cubic centimeters. This is quite sudden in evolutionary terms.

What was the effect of this voluminous increase in infant brain size on the birth process? The architecture of the pelvis, once it adapted to bipedalism, remained about the same for three million years. Obviously, much larger brains were not going to slide easily through a pelvis that had been designed for efficient bipedalism and small-brained newborns. The problem is architectural—the pelvis was designed as a scaffold for bipedal musculature and is as wide as it can be while still allowing women to walk efficiently. There is no way to retrofit the pelvis to accommodate a larger-brained infant. And so compromise had to come from the infant, and it did. First, there is a biological limit placed on infant brain development. Like all primates, human infants are born with a brain that takes up about 12 percent of their body weight; although destined to be highly encephalized—that is, proportionally biggerbrained as adults than other primates—yet start out with the relatively same-sized brain as any other primate. Again, we make up for this by an extremely fast rate of brain growth after birth. Second, prior to birth the bones of the skull are not fused and there is thus lots of room for smashing those bones together and molding the head as it squeezes through the pelvic passage. The "soft spots" on infant skulls, more correctly called "fontanels," are the areas where various skull bones meet—-often you can see the pulse of a heartbeat through the thin cranial membranes. In nonhuman primates these spots are almost totally fused, but in humans, they remain wide and flexible. The resulting 'cone-head" shape of the human newborn's head is simply nature's way of squeezing a child out with little damage to brain tissue.

[...]

And so we have the miracle of modern human birth—a painful, twisted journey that squeezes the infant head like Play-Doh and causes mothers unbelievable pain. And we also have all the pieces for the answer to why our infants are born so helpless. They are born with unfinished brains because the pelvis simply cannot be any wider or any bigger. If it were, women couldn't walk. Painful childbirth and helpless babies are an evolutionary compromise between selection for bipedalism, which came first. and later adult brain expansion.

Anthropologists Karen Rosenberg and Wenda Trevathan point out that the consequences are not just mechanical, they are also behavioral and social. The tight fit and tortuous route for human birth causes long and difficult labor for both the mother and the child. This trauma affects how the mother feels after birth, both physically and mentally. And infants come out rather exhausted and battered from this ordeal as well. The more than difficult process might account for the difference in style between human and nonhuman primate birth. A birth in a colony of Barbary macaques that was witnessed by two researchers, Vivika Ansorge and Kurt Hammerschmidt, was described as comparatively quick but not without pain.^° The mother, following the troop to the sleeping trees for the night, stopped several times and did stretches with her legs. a sort of dance that signaled something odd going on. She squatted. repeatedly touched her genital areas, and emitted low vocalizations which the researchers described as "moans." Eventually, she reached behind with her right arm and scooped up the baby that was coming out between her legs. She held it to her chest and it yelped. Within minutes the mother, rather dazed to be sure, moved on. There are very few descriptions of primate births because animals most often give birth at night or early in the morning. Humans, too, most often give birth in the early hours, but are hardly ever alone. Rosenberg and Trevathan suggest that the idea of attending a birth is actually an evolved strategy of our species that is necessary because human mothers are less equipped than monkey mothers to help in the process. The mother is in greater pain, the birth takes longer, and the infant comes out face down. She needs someone to catch the infant and clear its air passages. She needs someone to hand her the baby and later pull on the placenta if need be. Wenda Trevathan calls this "obligate midwifery," suggesting that we need to have attendants because the evolution of bipedalism and big babies left us no choice. And so our birthing is not just a biological event, but a social event as well. It relies on the help of family and friends, and emphasizes how important interpersonal interaction is to the human species, even when one of us first appears.