How to use this Page

By David Haig

A woman who gives birth to six children each with a 75% chance of survival has the same expected number of surviving offspring as a woman who gives birth to five children each with a 90% chance of survival. In both cases, 4.5 offspring are expected to survive. Because the large fitness gain from an additional child can compensate for a substantially increased risk of childhood mortality, women’s bodies will have evolved to produce children closer together than is best for child fitness.

Sleeping baby by Minoru Nitta. CC BY 2.0 via Flickr.

Offspring will benefit from greater birth-spacing than maximizes maternal fitness. Therefore, infants would benefit from adaptations for delaying the birth of a younger sib. The increased risk of mortality from close spacing of births is experienced by both the older and younger child whose births bracket the interbirth interval. Although a younger sib can do nothing to cause the earlier birth of an older sib, an older sib could potentially enhance its own survival by delaying the birth of a younger brother or sister.

The major determinant of birth-spacing, in the absence of contraception, is the duration of post-partum infertility (i.e., how long after a birth before a woman resumes ovulation). A woman’s return to fertility appears to be determined by her energy status. Lactation is energetically demanding and more intense suckling by an infant is one way that an infant could potentially influence the timing of its mother’s return to fertility. In 1987, Blurton Jones and da Costa proposed that night-waking by infants enhanced child survival not only because of the nutritional benefits of suckling but also because of suckling’s contraceptive effects of delaying the birth of a younger sib.

Blurton Jones and da Costa’s hypothesis receives unanticipated support from the behavior of infants with deletions of a cluster of imprinted genes on human chromosome 15. The deletion occurs on the paternally-derived chromosome in Prader-Willi syndrome (PWS). Infants with PWS have weak cries, a weak or absent suckling reflex, and sleep a lot. The deletion occurs on the maternally-derived chromosome in Angelman syndrome (AS). Infants with AS wake frequently during the night.

The contrasting behaviors of infants with PWS and AS suggest that maternal and paternal genes from this chromosome region have antagonistic effects on infant sleep with genes of paternal origin (absent in PWS) promoting suckling and night waking whereas genes of maternal origin (absent in AS) promote infant sleep. Antagonistic effects of imprinted genes are expected when a behavior benefits the infant’s fitness at a cost to its mother’s fitness with genes of paternal origin favoring greater benefits to infants than genes of maternal origin. Thus, the phenotypes of PWS and AS suggest that night waking enhances infant fitness at a cost to maternal fitness. The most plausible interpretation is that these costs and benefits are mediated by effects on the interbirth interval.

Postnatal conflict between mothers and offspring has been traditionally assumed to involve behavioral interactions such as weaning conflicts. However, we now know that a mother’s body is colonized by fetal cells during pregnancy and that these cells can persist for the remainder of the mother’s life. These cells could potentially influence interbirth intervals in more direct ways. Two possibilities suggest themselves. First, offspring cells could directly influence the supply of milk to their child, perhaps by promoting greater differentiation of milk-producing cells (mammary epithelium). Second, offspring cells could interfere with the implantation of subsequent embryos. Both of these possibilities remain hypothetical but cells containing Y chromosomes (presumably derived from male fetuses) have been found in breast tissue and in the uterine lining of non-pregnant women.

David Haig is Professor of Biology at Harvard University. he is the author of “Troubled sleep: Night waking, breastfeeding and parent–offspring conflict” (available to read for free for a limited time) in Evolution, Medicine, and Public Health. The arguments summarized above are presented in greater detail in two papers that recently appeared in Evolution, Medicine, and Public Health.

Evolution, Medicine, and Public Health is an open access journal, published by Oxford University Press, which publishes original, rigorous applications of evolutionary thought to issues in medicine and public health. It aims to connect evolutionary biology with the health sciences to produce insights that may reduce suffering and save lives. Because evolutionary biology is a basic science that reaches across many disciplines, this journal is open to contributions on a broad range of topics, including relevant work on non-model organisms and insights that arise from both research and practice.

Subscribe to the OUPblog via email or RSS.
Subscribe to only science and medicine articles on the OUPblog via email or RSS.

The post Breastfeeding and infant sleep appeared first on OUPblog.

        

Related Stories

• Are you a tax expert?
• BICEP2 finds gravitational waves from near the dawn of time
• Voluntary movement shown in complete paralysis

 

Today we have two books from the Little Masters, Baby Lit® Books collection from publisher Gibbs Smith, author Jennifer Adams, and illustrator Alison Oliver.  The first, A Christmas Carol by Charles Dickens, is a coloring primer that will paint this week’s big day red and green. Then Bram Stoker’s Dracula, a counting primer, will put [...]

By Professor Jane Edwards

What does the baby have to learn in these first 12-18 months (before they can speak)? The list  includes what you do with your eyes when with another, how long to hold a mutual gaze, what turn-off head movements work, and with whom, how close you should let the other come to you… how to read body positions… how to enter into turn taking when vocalizing with another… how to joke around, negotiate escalate, back off… make friends, and so on.
Daniel Stern, Forms of Vitality (OUP, 2010) p. 110-111

As a music therapy scholar, teacher, and practitioner for more than 20 years, I have been able to learn from many sources about the crucial role our early years play in our lives. The ability to reflect on challenges experienced in our adult lives by linking back to childhood experiences is an essential aspect of the way that many music therapists practice. Rather than using descriptions of family histories to apportion blame, the therapist tries to understand the current experience of the patient and their worldview through the lens of past experience, to see if there is some way to make sense of self-destructive behaviours, or difficulties experienced in creating meaningful and satisfying relationships with others.

I began my early music therapy practice in mental health services and in nursing homes, working with people diagnosed with Alzheimer’s Disease or other types of dementia. Many people, whether in group or individual music therapy programmes, offered reflections on their early life, and described aspects of their parents’ availability or unavailability; referring to the quality of these first relationships in ways that helped me to understand something of what might have been unresolved or unsatisfying for them. Eventually I found myself very keen to work with people much earlier in life to see whether music therapy could ameliorate some of the issues my older patients were facing.

Although I worked in paediatric music therapy for seven years at a children’s hospital, it was only when I was writing the first proposal to found the (now) international parent-infant support programme Sing & Grow that I had the chance to bring all of my past experience to bear: to make a case for the importance of promoting loving, playful, and nurturing interactions between parents and infants where vulnerability was in evidence. Through my work in this field, I have become increasingly aware of an unrecognised field of practice in music therapy: parent-infant work. This involves the referral of vulnerable parents to a music therapy service. Parents usually attend with their infants and the music therapist provides a safe and accepting space in which the parent and infant pair or group can be encouraged to play and interact in supportive and mutually satisfying ways. This is not always ‘music’ as it might be generally understood; rather it is a musical way of interacting that the therapist encourages.

When adults speak to infants we use particular ways of interaction that seem to be the same across the world. But we should ask why do we use such an exaggerated, playful, and musical way of speaking to infants? The obvious answer is because the infants like it — they raise their eyebrows, fix their gaze on the speaker’s face, and sometimes smile quite quickly on hearing us say ‘ooohhh whooo is my little baaaby?’ This is especially true if the speaker is a family member but it also can occur in new encounters when the conversational partner knows and can offer this communication in a playful and experimental way.  However, there are many more powerful scientific and theoretical findings that indicate how this type of interaction builds the bonds of trust and love between parents and infants.

Work by psychobiologist Colwyn Trevarthen, the ethologist Ellen Dissanayake, and researcher Sandra Trehub and her team at the University of Toronto, has paved the way in showing how the functions of this interaction have less to do with entertaining and engaging the baby and are more aligned with the infant’s ability to evoke and interpret these signals from adults and their siblings within weeks of birth. For me, and for the researchers mentioned above, these interactions are easily identified as musical. Observations of the nature of these interactions between parents and infants led Stephen Malloch to coin the term ‘Communicative Musicality’, to capture the unique pitch and rhythmic structures that communicative partners use.

This type of interaction is, as the quote from Stern at the opening attests, playful, rich, and highly involved. It teaches the many skills we need in being able to be with people successfully in intimate relationships, in relationships involving teachers and students, and in work groups. When we do not have adequately rich and supported experiences of attachment in infancy there can be lifelong consequences. Therefore, offering support to parents and infants in difficulty can provide long term benefits. Music therapy is uniquely poised to make a useful contribution to this work as infants are receptive to musical and music-like interactions from sensitive and responsive adults.

Professor Jane Edwards is an Associate Professor at the University of Limerick where she directs the Music & Health Research Group and is co-ordinator of the MA in Music Therapy in the Irish World Academy of Music & Dance. She was formerly a guest professor at the University of the Arts in Berlin (2004-2011). She is President of the International Association for Music & Medicine. She has published extensively in the field of music therapy including Music Therapy and Parent-Infant Bonding (OUP, 2011), and is sole editor for the first Oxford Handbook of Music Therapy (forthcoming).

Subscribe to the OUPblog via email or RSS.
Subscribe to only music articles on the OUPblog via email or RSS.
Subscribe to only psychology articles on the OUPblog via email or RSS.
View more about this book on the  

Image credit: ‘Mother Kissing Baby’ By Vera Kratochvil (public domain via Wikimedia Commons).

We really lucked out with our first born, nicknamed Cuddle-Bear. He is an easy tempered child who tends to be fairly content with life as it rolls along. Cuddle-Bear started sleeping thru the night at 3 weeks and has always had a healthy appetite. He didn’t spit up very much and at the worst, he was difficult to burp. Even the beginning of the ‘Terrible Twos’ hasn’t been all that difficult. His temper-tantrums, while quite loud, are generally non-violent and infrequent.

If how things are going right now with Snuggle-Bug (the new baby) is any indication of how the next 18 years are going to be, I think I should either invest in a wig or get ready for having a headful of grey hair before I am 50. In the baby’s defense, part of the problem is he is somewhat colicky. Colic, which sounds like some quaint expression for something akin to uncontrollable hiccoughs to the uninitiated, is the bane of my efforts to get some sleep. As soon as the sun sets, Snuggle-Bug starts getting fussy. It just gets more intense as the night goes on.

Fortunately, he doesn’t scream his way thru feedings, though I feel like he’s trying to make me deaf when it’s time to burp him. (If you want to really offend your colicky baby, take that bottle away mid-feeding to burp the child. They’ll scream almost as loud as a toddler in their fury and make you need to change that clean diaper in the process. If you’re a masochist, try it out for fun. Your child will reward you with punishing cries everytime.) It seems as though there are only two ways to calm Snuggle-Bug during the night. One is to swaddle him tightly in a receiving blanket. The other is to rock with him in the rocking chair and sing myself hoarse while making sure the pacifier is securely in place.

Sometimes, the two need to be combined. This is fine and dandy, except for the fact that I have a toddler that I need to be up with during the day. Snuggle-Bug’s temper during the day is just as intense as it is during the night. I don’t claim to understand it, but I’m fairly certain that small children have some form of self-sustaining power source of an arcane nature within them. It is the only explanation as to how they can be up all night screaming their little lungs out and then proceed to be up screaming most of the day if they’re not in your arms or getting fed. Toddlers are not quite as bad, but that’s because they will sleep somewhat. In their case, the power source is used less for producing ear splitting decibels of noise and more for perpetual motion.

I find myself hoping and praying that Snuggle-Bug will sleep thru the night soon. I really don’t want the colic to last for 3 to 6 months, which the books claim is usually the longest time it takes for it to pass. I am pretty sure that I’ll be a zombie by 3 months with out a few decent nights of sleep and I’m afraid to think about how I’ll be if it takes 6 months or longer for this to pass. The thing I have to admit I really hate is not the fact that Snuggle-Bug is colicky. It’s the fact that out of everyone in my home, I am the only one who is awakened by it. My husband and Cuddle-Bear sleep right thru the screaming fits just as if they don’t happen.

I would find it a little easier to bear if I wasn’t the only one who was awakened by this. Sure, I suppose I could say that Snuggle-Bug is awakened by it, but I don’t know if that counts. After all, he is the one waking me up. All that effort the baby puts into his screaming, however, makes me feel a bit wary about the next 18 years. He has a temper that just might be worse then mine on a bad day along with a stubborn streak like his father. I suspect that Snuggle-Bug’s temper-tantrums are going to approach legendary status and I’m going to be wishing for the bouts of colic. Am I a fool for dreading this even as I wish the colic would end soon?

We really lucked out with our first born, nicknamed Cuddle-Bear. He is an easy tempered child who tends to be fairly content with life as it rolls along. Cuddle-Bear started sleeping thru the night at 3 weeks and has always had a healthy appetite. He didn’t spit up very much and at the worst, he was difficult to burp. Even the beginning of the ‘Terrible Twos’ hasn’t been all that difficult. His temper-tantrums, while quite loud, are generally non-violent and infrequent.

If how things are going right now with Snuggle-Bug (the new baby) is any indication of how the next 18 years are going to be, I think I should either invest in a wig or get ready for having a headful of grey hair before I am 50. In the baby’s defense, part of the problem is he is somewhat colicky. Colic, which sounds like some quaint expression for something akin to uncontrollable hiccoughs to the uninitiated, is the bane of my efforts to get some sleep. As soon as the sun sets, Snuggle-Bug starts getting fussy. It just gets more intense as the night goes on.

Fortunately, he doesn’t scream his way thru feedings, though I feel like he’s trying to make me deaf when it’s time to burp him. (If you want to really offend your colicky baby, take that bottle away mid-feeding to burp the child. They’ll scream almost as loud as a toddler in their fury and make you need to change that clean diaper in the process. If you’re a masochist, try it out for fun. Your child will reward you with punishing cries everytime.) It seems as though there are only two ways to calm Snuggle-Bug during the night. One is to swaddle him tightly in a receiving blanket. The other is to rock with him in the rocking chair and sing myself hoarse while making sure the pacifier is securely in place.

Sometimes, the two need to be combined. This is fine and dandy, except for the fact that I have a toddler that I need to be up with during the day. Snuggle-Bug’s temper during the day is just as intense as it is during the night. I don’t claim to understand it, but I’m fairly certain that small children have some form of self-sustaining power source of an arcane nature within them. It is the only explanation as to how they can be up all night screaming their little lungs out and then proceed to be up screaming most of the day if they’re not in your arms or getting fed. Toddlers are not quite as bad, but that’s because they will sleep somewhat. In their case, the power source is used less for producing ear splitting decibels of noise and more for perpetual motion.

I find myself hoping and praying that Snuggle-Bug will sleep thru the night soon. I really don’t want the colic to last for 3 to 6 months, which the books claim is usually the longest time it takes for it to pass. I am pretty sure that I’ll be a zombie by 3 months with out a few decent nights of sleep and I’m afraid to think about how I’ll be if it takes 6 months or longer for this to pass. The thing I have to admit I really hate is not the fact that Snuggle-Bug is colicky. It’s the fact that out of everyone in my home, I am the only one who is awakened by it. My husband and Cuddle-Bear sleep right thru the screaming fits just as if they don’t happen.

I would find it a little easier to bear if I wasn’t the only one who was awakened by this. Sure, I suppose I could say that Snuggle-Bug is awakened by it, but I don’t know if that counts. After all, he is the one waking me up. All that effort the baby puts into his screaming, however, makes me feel a bit wary about the next 18 years. He has a temper that just might be worse then mine on a bad day along with a stubborn streak like his father. I suspect that Snuggle-Bug’s temper-tantrums are going to approach legendary status and I’m going to be wishing for the bouts of colic. Am I a fool for dreading this even as I wish the colic would end soon?