Barbara J. King

Friday Animal Blog

Co-Sleeping: Monkeys Do It, Apes Do It; Should We Do it Too?

November 26, 2010

Co-Sleeping: Monkeys Do It, Apes Do It; Should We Do it Too?

To most of us, it’s a behavior that comes as naturally as breathing: When it’s a baby’s bedtime, we put carry her to her room, give her a kiss, and turn on the infant monitor. Through the evening we’ll check on her, and tiptoe around hoping that she sleeps through the night. When she does sleep on her own a goodly number of hours, we broadcast the good news with friends and family- she’s on the way towards independence!

But wait a minute. Why should we expect our littlest ones to sleep in isolation? Backing off from our cultural norms, doesn’t it seem a little strange?

After all, look at what other primates do. Lemurs of Madagascar, squirrel monkeys of Brazil, baboons and chimpanzees of Tanzania- in all these species, indeed in almost all nonhuman primate species, babies cling round-the-clock to mom, breast-feeding and sleeping at will. This intense day-and-night closeness lasts for months and sometimes years.

And mom-baby co-sleeping is not limited to our nonhuman kin. Some form of co-sleeping (bed-sharing or baby in a crib near the mom) is practiced broadly around the world. When in North American, European or Australian culture we bed down our child on her own, we diverge not only from millions of years of evolution but also from robust cross-cultural patterns.

Thanks to the work of biological anthropologist James McKenna and colleagues, the evolutionary perspective on co-sleeping is well known within science circles. I’m not blogging on this topic because it’s breaking science news, but instead because it’s a fabulous example of how an evolutionary perspective can help us think hard about our behavioral choices today.

In 2005, McKenna and Thomas McDade published a peer reviewed article called “Why babies should never sleep alone” in the journal Paediatric Respiratory Reviews (No. 6, 134-152-- email me if you’d like a copy). The pair explains that baby primates are not meant to be isolated, and when they are, their lungs are likely to shriek out a protest:

The emotional responses by infants and children
to resist parental isolation by crying and protesting are
probably innate and adaptive, since separation from the
caregiver most certainly meant rapid death for infants and
children in the environments within which childhood sleep
and emotions evolved.

Co-sleeping, McKenna and McDade note, isn’t an automatic good. When alcohol is consumed, or illegal drugs used, even when the mother smokes cigarettes, bed-sharing may be unsafe for the baby.

Yet when done responsibly, the benefits may be large. Human babies’ central nervous systems—including their brains and breathing systems-- are unfinished at birth. Women can birth a large-brained baby only because the baby’s brain grows especially intensively for a year outside the womb. Because of the neurological immaturity so evident right at birth, infants are at risk for Sudden Infant Death Syndrome (SIDS). Co-sleeping may reduce that risk because episodes of mutual arousal by mom and baby during the night help to regulate the baby’s breathing, and because in this context the baby sleeps supine, face up and ready for breastfeeding (and thus not in the most dangerous position, on its stomach).

McKenna and McDade conclude:

The general hypothesis that co-sleeping (at least in the
form of a committed caregiver’s proximity i.e,. roomsharing)
reduces SIDS among some SIDS prone infants is confirmed
by studies showing that roomsharing in the presence of an
active caregiver saves lives.

What an amazing public-health message! Happily, McKenna doesn’t write only for doctors and other academics. He’s taken his message on NBC’s Today Show, for example, and has written a popular book on co-sleeping called Sleeping with Your Baby: A Parent’s Guide to Co-sleeping.

Public outreach in anthropology is, I believe, incredibly important. But how effective is it? I’m curious to know: Have you in recent years read, or learned from radio or TV, about this evolutionary perspective on co-sleeping (starring monkeys and apes)? If so, what do you make of it?


  1. November 26, 2010 9:29 AM EST
    The theory about SIDS as a consequence of babies sleeping alone has been around for a long time - I heard a talk about it at least 15 or 20 years ago. The lecturer mentioned that SIDS deaths are almost non-existent in cultures that cosleep, and that babies with slightly more incomplete brain development seemed to use mom's respiration like a metronome to keep their own rhythm going. So sad that this idea has taken such a long time to get attention!!
    - Melanie Bond
  2. November 26, 2010 9:48 AM EST
    Yes I do think the idea is from the '90s, though the hard data to support the hypothesis about co sleeping and reduced SIDS are quite a bit newer... McKenna's work in the sleep lab is extraordinary, getting physiological/quantitative data on mon-baby pairs. I wonder whether the practice is really catching on, or if the old unfounded worries about rolling over onto the baby, or causing a dependent child, continue.
    - Barbara J. King
  3. November 26, 2010 4:05 PM EST
    Some say that making the baby sleep alone is a matter of gender and power. When the baby sleeps alone, preferably in a separate room, the father (or whatever male claims the mother as his own) has easier and quicker access to the mother than when she sleeps with the baby, nursing on demand.
    - Margaret Trawick
  4. November 26, 2010 4:27 PM EST
    Our kids slept with us until they didn't want to any more. I don't know where the concept that you will create needy, dependent children if you provide them with natural comfort and stability comes from! It seems more likely that by pushing children away, leaving them alone, and not responding to their needs for close contact with their mother/parents when they are small, you make children insecure and thus more needy and clingy. My two are young adults now and I've always had people comment on how mature and independent they are - even when they were 3 or 4 years old and still sleeping with us. I'm sure there are many factors leading to healthy and mature children in addition to co-sleeping, but I think co-sleeping is one way to help children feel secure and nurtured when they most need it. I hope this information can get out somehow to change cultural habits in the US.
    - Linda Raftree
  5. November 27, 2010 6:49 PM EST
    Same with me, Linda. My kids were very independent from a young age, and each of them slept in the same bed as me and my husband until they were about five.
    - Margaret Trawick
  6. November 27, 2010 6:58 PM EST
    The comments from personal experience are key, and very welcome. As I see it, co-sleeping and breast-feeding are inextricably intertwined. I've just posted on my Facebook page a video of the TSA harrassing a young mother trying to take breastmilk onto a flight without its going through the xray scanner- exactly as TSA guidelines say it can. What happens is pretty disturbing. It shows how far our society has to go in understanding these natural behaviors. The video is here (you will have to cut and paste the URL)
    - Barbara J. King
  7. November 29, 2010 7:44 AM EST
    Agreed ref co-sleeping and breast feeding. I have had many friends who as new mothers are somewhat miserable from lack of sleep. I keep saying 'why not keep the baby in bed with you?' but they are quite resistant to that idea, saying no, 'I just need to get the baby on a schedule'. Another aspect in a few of those cases is that they are actually co-parenting (instead of pretending they are) and the father gets up sometimes at night with the baby. I do think that breastfeeding can make it challenging for fathers who want to more equally share in the parenting at an early age...
    - Linda Raftree
  8. December 1, 2010 1:10 AM EST
    I was a zoo keeper when I was having babies. For a primate to put a baby down and walk away from it was unquestionably maternal neglect and a huge danger sign that the baby would not long survive without our intervention. So of course our babies slept in bassinets next to us. There's also good primate research that mothers who are always available produce more independent babies, the opposite of what my grandmother believed. I do not understand the modern reluctance to sleep next to the baby, or to pick the baby up, for that matter. What's with all this stroller time?
    - Ann Littlewood
  9. December 1, 2010 8:54 AM EST
    I'm particularly happy to hear from a former primate keeper because so much of my own thinking on this issue has been shaped by time with monkeys and apes (esp. in Amboseli, Kenya, and later at the National Zoological Park Ape House). Ann, I'd love to know where you'd worked. I've long taken note of Jeanne Altmann's finding on wild baboons about a continuum of primate mothering- from more restrictive to more laissez faire. The mothers termed laissez faire let their kids explore more and the young ones seemed to become independent earlier: but obviously, the 'laissez faire' mothers were still involved in breast feeding and co sleeping! It's just a primate given. I think we're dealing with deeply rooted cultural myths in our society but on the other hand, I sympathize with women who have multiple kids and demanding jobs and no extended families to help. In that context it may seem overwhelmingly harder to co sleep etc. I wouldn't want anyone to feel guilty if they can't manage to achieve primate ideals!
    - Barbara J. King

Selected Works

Why are animals so irresistible to us? Why do we live with and care so deeply about them? From the famous "art caves" of ice-age Europe, to the ancient villages where animals were first domesticated, to stories of apes, whales, dogs, and cats doing fascinating things today, King weaves together a scenario about the animal-human bond that encompasses our past, present and future.
Can scientists discover a prehistory of religion just as they have traced the evolution of technology, language, and art? What does compassion in chimpanzees, or burial patterns in our human ancestors and Neanderthals, tell us about the origins of religion? In Evolving God, named a Top Ten Religion Book for 2007 by the American Library Association, Barbara King explores these questions.
How do chimpanzees, bonobos, and gorillas-- the African apes -- communicate using body postures and gestures? Using her many years of experience studying these apes, Barbara King answers this question in a book that offers a new perspective on the evolution of language.