People spend a third of their lives asleep. And we do not sleep in random ways. How we sleep, with whom we sleep, and where we sleep is molded both by culture and custom, traditions handed down through generations. For most of human history, babies and children slept with their mothers, or perhaps with both parents. Our distant ancestors lived in small groups that subsisted by hunting and gathering, and it is safe to assume that these bands did not have separate sleeping quarters for parents and children in their temporary shelters. It wasn't until 200 years ago that a few cultures began to construct dwellings with more than one room, and even today, such sleeping privacy is rare except in more affluent societies. The majority of people around the world still live in one-room shelters where all activities take place.
Anthropologist John Whiting also found a simple association between climate and parent-child cosleeping (among other behaviors). Evaluating 136 societies, Whiting outlined four kinds of typical household sleeping arrangements: 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 polygamous, 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 hu-man population.
In almost all cultures around the globe, babies sleep with an adult, while older children sleep with parents or other siblings. It is only in industrialized Western societies such as those in North America and some parts of Europe that sleep has become a private affair. The West, in fact, stands out from the rest of humanity in the treatment of its children during sleep. In one study of 186 nonindustrial societies, children sleep in the same bed as their parents in 46 percent of the nonindustrial cultures, and in a separate bed but in the same room in an additional 21 percent. In other words, in 67 percent of the cultures around the world, children sleep in the company of others. More significantly, in none of those 186 cultures do babies sleep in a separate place before they are at least one year old. In another survey of 172 societies, all infants in all cultures do some cosleeping at night, even if only for a few hours. The US consistently stands out as the only society in which babies are routinely placed in their own beds and in their own rooms.
Anthropologist Gilda Morelli compared the sleeping arrangements and nighttime habits of parents in the US with a group of Mayan Indians in Guatemala. The Mayan babies slept with their mothers in all cases for the first and sometimes the second year. In more than half the cases, the father was there as well, or he was sleeping with older children in another bed. Mayan mothers made no special note of feeding at night because they simply turned and made a breast available when the baby cried with hunger, probably while the mothers were still fast asleep. For the comparative US group, three babies were placed in a separate room to sleep from the time they were born, and none of the 18 subjects slept in the parents' bed on a regular basis. By three months of age, 58 percent of the babies were already sleeping in another room; and by six months of age, all but three had been moved out to a separate room. Not surprisingly, 17 of the 18 American parents reported having to stay awake for nighttime feedings.
Differences in attitude toward sleep in general were equally clear between the two cultures. American parents used lullabies, stories, special clothing, bathing, and toys to ritualize the sleep experience, whereas Mayan parents simply let their babies fall asleep when they did, with no folderol. When the researcher explained to the Mayan mother how babies were put to bed in the US, they were shocked and highly disapproving, and expressed pity for the American babies who had to sleep alone. They saw their own sleep arrangements as part of a larger commitment to their children, a commitment in which practical consideration plays no part. It did not matter to them if there was no privacy, or if the baby squirmed at night - closeness at night between mother and baby was seen as part of what all parents do for their children.
Conversely, the American parents who slept with their babies on a regular basis said they did so for "pragmatic" reasons (presumably for breastfeeding and comforting a fretful baby), although they acknowledged that cosleeping seemed to foster attachment. Unlike the Mayans, they often found this attachment to be worrisome and somehow emotionally or psychologically unhealthy. They moved their babies out of the parental room as soon as possible, usually by six months; and they expressed the need to guide the child down a path of independence, as well as a desire for their own privacy. They also felt such separation would be less traumatic if done early rather than later. As one mother put it, "I am a human being, and I deserve some time and privacy to myself." Many mothers also have been told by pediatricians or childcare experts that sleeping alone in a bassinet or crib is safer for the baby, and so they follow this advice, assuming they are doing the right thing.
Differences in attitude among cultures can perhaps be most clearly seen in work on immigrants from one culture to another; infant sleep patterns, it turns out, are one of the last traditions to change under pressure from the adopted country. In England, Asian parents - that is, people of Indian, Pakistani, and Bangladeshi origin - continue to sleep with their babies even when this is not the accepted pattern or the one advocated by British health care. And in the US, where solitary sleep is advocated by pediatricians and the larger society, ethnic pockets remain in which sleeping with the baby is the accepted pattern; minorities that live by nonwhite rules also regularly cosleep. In one study of Hispanic-Americans in East Harlem in New York City, 21 percent of the children from six months to four years of age slept with their parents, as compared to 6 percent of a matched sample of white middle-class children. Eighty percent of the Hispanic children shared the same room with their parents, and this sharing was not due solely to space constraints.
Recent immigrants are not the only group that differs in their sleeping arrangements with their children. In a comparison of whites and African Americans, 55 percent of the white parents and 70 percent of the black parents said they coslept with their babies. For whites, cosleeping with their children took place primarily when babies were perceived to have sleeping problems - defined as waking during the night - or due to a mother's ambivalence toward the parenting role. In this and other studies, cosleeping in white families was usually a last-resort attempt to soothe a troubled child or fix a troubled parent-offspring relationship. For black parents, cosleeping was seen as a normal pattern and had nothing to do with fixing a troubled sleep history or a problematic relationship.
In Appalachia or eastern Kentucky, cosleeping in infancy and childhood is the norm, as it has been for hundreds of years. Although the people of this area are not an ethnic minority or recent immigrants, they do represent a cohe- sive population that has been resistant to change. Historians note that in colonial times on the eastern seaboard, several people slept in the same bed - it was the only way to sleep in such small houses. But when new ideas about privacy began to appear in the 19th century, housing reflected those changes, and suddenly there were private sleeping rooms, first in public houses and then in private homes. The people of Appalachia, descendants of that more colonial tradition, continued the communal sleeping arrangement and still refuse to place babies alone even when there is plenty of room. Contrary to the advice given by pediatricians in the area, these mothers place their babies in the parental bed because they believe in their particular parenting ideology.
As anthropologist Susan Abbott points out, "[Cosleeping] is not some kind of quaint hold-over from an archaic past, nor is it pathological in its constitution or outcome for the majority of those who experience it. It is a current, well-situated pattern of child rearing that is withstanding the onslaught of advice by contemporary childcare experts."
The point is to make a tightly knit family and keep children close. Seventy-five-year-old Verna Mae Sloane writes of motherhood in Appalachia: "How can you expect to hold on to them in life if you begin by pushing them away?"
Why is cosleeping important? Science is just now learning the answer to that question. No one yet knows why animals sleep, but we do have a pretty good idea how sleep occurs. Like most physical states, sleep involves a number of biological or physiological mechanisms. Sleep is controlled by the primitive brain stem, which sends messages to and from the heart, the lungs, muscles around the diaphragm and ribs, and hormone- producing organs - all systems that monitor and regulate the choreography of sleep. In sleep, just as during times of wakefulness, adult humans shift through periods of controlled neocortical-driven breaths and automatic brainstem-initiated breaths. Adults are able to manage the shift between these types, but infants do it less easily. Infants are born with neurologically unfinished brains. They don't develop the ability to easily navigate types of breathing until they are at least three to four months old, and the sleep patterns of newborns reflect this. As mentioned earlier, they are unable to consolidate periods of sleep and don't distinguish between day and night; they also spend more time in REM sleep than adults do.
When sleeping with her mother, a baby reacts to her movements and goes through any number of changes in sleep stages, far more than when the infant sleeps alone, practicing the transitions from one kind of breathing to another. Left alone, babies must steer through night sleep with little training, and no external environmental stimuli or cues. Most babies eventually develop the skill to shift between types of breathing as their brains develop. But for some infants, such shifts may be harder; they could benefit from the external metronome of parental breathing. Cosleeping, with all its entwined movements through various levels of sleep, and its physical checkpoints, may be exactly what nature intended to ensure babies survive through the night as well as learn how to sleep and breathe on their own.
Most parents in Western culture, by opting not to cosleep, have thus altered the physical parent-baby interaction during sleep hours. But it is important for parents who have done so to realize that they have opted for this arrangement because of cultural reasons, not out of biological appropriateness. What these well-meaning parents do not realize is that they might also be putting their babies unnecessarily at risk.
Infant needs and parental responses to those needs do, after all, constitute a dynamic, co-evolving system, a system that was, and is even now, being shaped by natural selection to maximize infant survival and improve parental reproductive success. Culture may change, and society might progress, but biology is modified at a much slower rate. Babies are still stuck with their Pleistocene biology despite our modern age, and no amount of technological devices or bedtime routines will change that. What babies need from parents is to be part of that interactive parent-baby system that evolved for good evolutionary reasons, and which is a biological necessity even today.
Written by Meredith F. Small, professor of anthropology at Cornell University. She is the author of Female Choices: Sexual Behavior of Female Primates and What's Love Got to Do with It? The Evolution of Human Mating. This article is excerpted from her book, Our Babies, Ourselves (Anchor Books, 1998).