Carrying human infants - An evolutionary heritage

Infant carrying: Associations with parental reflective functioning, parental bonding and parental responses to infant crying

Infant carrying may have beneficial effects on the parent-infant relationship but only limited research has been conducted in this area. Therefore, the main aim of the current study was to investigate whether infant carrying is associated with parental reflective functioning, parental bonding, and parental (emotional) and behavioral responses to infant crying, key elements within the parent-infant relationship, promoting infant development. Parents reporting high levels (N = 389) of infant carrying (six times a week or daily) and parents reporting low levels (N = 128) of infant carrying (less than once a week or not at all) who participated in an online survey about the developing parent-infant relationship in Germany were included in the present study. Standardized questionnaires were used to assess parental reflective functioning, parental bonding impairments, and emotional responses to infant crying. Further insensitive (non-responsive and hostile) behaviors in response to infant crying were assessed. Parents with high levels of infant carrying showed better parental reflective functioning, lower parental bonding problems, less negative emotions, and less insensitive behaviors in response to infant crying.

'Either something's wrong, or I'm a terrible parent': A systematic review of parent experiences of illness-related interpretations for unsettled babies

AIMS

To explore parents' experiences of unsettled babies and medical labels.

DESIGN

Qualitative systematic review, thematic synthesis and development of a conceptual model.

REVIEW METHODS

Systematic review and thematic synthesis of primary, qualitative research into parents' experiences of unsettled babies <12 months of age. 'Unsettled' was defined as perception of excessive crying with additional feature(s) such as vomiting, skin or stool problems. The Critical Appraisal Skills Programme (CASP) checklist was used to assess trustworthiness.

DATA SOURCES

Structured searches completed in CINAHL, Medline, Embase, PsychINFO and CochraneCT on 23 March 2022 and rerun on 14 April 2023.

RESULTS

Ten eligible studies were included across eight countries contributing data from 103 mothers and 24 fathers. Two analytical themes and eight descriptive themes were developed. Firstly, parents expressed fearing judgement, feeling guilty and out of control as a result of babies' unsettled symptoms and seeking strategies to construct an 'Identity as a "Good Parent"'. This desire for positive parenting identity underpinned the second analytical theme 'Searching for an explanation' which included seeking external (medical) causes for babies' unsettled behaviours.

CONCLUSION

Parents can become trapped in a cycle of 'searching for an explanation' for their baby's unsettled behaviours, experiencing considerable distress which is exacerbated by feelings of guilt and failure.

IMPACT AND IMPLICATIONS FOR PATIENT CARE

Insight gained from this review could inform interventions to support parents, reducing inaccurate medicalization. Health visiting teams supporting parents with unsettled baby behaviour could focus on supporting a positive parenting identity by managing expectations, normalizing the continuum of infant behaviours, reducing feelings of guilt or uncertainty and helping parents regain a feeling of control.

REPORTING METHOD

ENTREQ guidelines were adhered to in the reporting of this review.

PATIENT OR PUBLIC CONTRIBUTION

Parent input was crucial in the design phase; shaping the language used (e.g., 'unsettled babies') and in the analysis sense-checking findings.

Babywearing Reduces Urges to Use Substances in the Postpartum Period Among Mothers With OUDs

OBJECTIVES

While pregnancy presents a strong motivation to seek and comply with Opioid Use Disorder (OUD) treatment, the risk for relapse during the postpartum period is high. The purpose of the present study was to examine the impact of babywearing while admitted to the NICU on urges to use substances within 9 months of childbirth.

METHODS

Mothers with a history of OUD (N = 47, Mage = 28.91, SD = 5.14; 48.9% White, 19.1% Latinx) and their newborns were randomly assigned to the intervention (babywearing) or control (infant rocker) condition while admitted to a NICU. Interviews occurred every 3-months. Participants reported their strong desire or urge to use substances since the last interview. Approximately 68.1% had urges within 9 months. At 3 months, participants were categorized as: never babywore (0 h, N = 18), some babywearing (1-44 h, N = 13), consistent babywearing (45+ hours, i.e., minimum of 3.5 h per week, N = 16).

RESULTS

Condition X2(2, N = 47)=12.55, p < 0.001, Phi = 0.52 and babywearing category, X2(2, N = 47)=6.75, p = 0.034, Phi = 0.38 significantly predicted urges to use. Mothers in the intervention condition were more likely to report no urges to use: 56.5% had no urges (43.5% had urges) compared to 8.3% of control mothers (91.7% had urges). Mothers who consistently babywore had significantly fewer urges to use (43.8% had urges) compared to mothers who never babywore (83.3% had urges).

CONCLUSIONS FOR PRACTICE

There is a critical window to capitalize on mothers' desire to abstain from substance use. Babywearing, and specifically babywearing at least 30 min a day, reduced urges to use substances post-partum, a factor associated with relapse.

A century of exercise physiology: concepts that ignited the study of human thermoregulation. Part 4: evolution, thermal adaptation and unsupported theories of thermoregulation

This review is the final contribution to a four-part, historical series on human exercise physiology in thermally stressful conditions. The series opened with reminders of the principles governing heat exchange and an overview of our contemporary understanding of thermoregulation (Part 1). We then reviewed the development of physiological measurements (Part 2) used to reveal the autonomic processes at work during heat and cold stresses. Next, we re-examined thermal-stress tolerance and intolerance, and critiqued the indices of thermal stress and strain (Part 3). Herein, we describe the evolutionary steps that endowed humans with a unique potential to tolerate endurance activity in the heat, and we examine how those attributes can be enhanced during thermal adaptation. The first of our ancestors to qualify as an athlete was Homo erectus, who were hairless, sweating specialists with eccrine sweat glands covering almost their entire body surface. Homo sapiens were skilful behavioural thermoregulators, which preserved their resource-wasteful, autonomic thermoeffectors (shivering and sweating) for more stressful encounters. Following emigration, they regularly experienced heat and cold stress, to which they acclimatised and developed less powerful (habituated) effector responses when those stresses were re-encountered. We critique hypotheses that linked thermoregulatory differences to ancestry. By exploring short-term heat and cold acclimation, we reveal sweat hypersecretion and powerful shivering to be protective, transitional stages en route to more complete thermal adaptation (habituation). To conclude this historical series, we examine some of the concepts and hypotheses of thermoregulation during exercise that did not withstand the tests of time.

Breastfeeding sick children in hospital: Exploring the experiences of mothers in UK paediatric wards

There is a paucity of literature exploring the challenges of breastfeeding sick children in hospital. Previous research has focused on single conditions and hospitals which limits understanding of the challenges in this population. Although evidence suggests that current lactation training in paediatrics is often inadequate, it is unclear where the specific training gaps are. This qualitative interview study of UK mothers aimed to explore the challenges of breastfeeding sick infants and children on a paediatric ward or paediatric intensive care unit. From 504 eligible respondents, a sample of 30 mothers of children aged 2-36 months with various conditions and demographic backgrounds was purposively chosen, and a reflexive thematic analysis undertaken. The study identified previously unreported impacts such as complex fluid needs, iatrogenic withdrawal, neurological irritability and changes to breastfeeding behaviour. Mothers described breastfeeding as emotionally and immunologically meaningful. There were many complex psychological challenges such as guilt, disempowerment, and trauma. Wider struggles such as staff resistance to bedsharing, inaccurate breastfeeding information, lack of food and inadequate breast pump provision made breastfeeding more challenging. There are numerous challenges related to breastfeeding and responsively parenting sick children in paediatrics, and these also impacted maternal mental health. Staff skill and knowledge gaps were widespread, and the clinical environment was not always conducive to supporting breastfeeding. This study highlights strengths in clinical care and provides insight into what measures are perceived as supportive by mothers. It also highlights areas for improvement, which may inform more nuanced paediatric breastfeeding standards and training.

Human cooperation and evolutionary transitions in individuality

A major evolutionary transition in individuality involves the formation of a cooperative group and the transformation of that group into an evolutionary entity. Human cooperation shares principles with those of multicellular organisms that have undergone transitions in individuality: division of labour, communication, and fitness interdependence. After the split from the last common ancestor of hominoids, early hominins adapted to an increasingly terrestrial niche for several million years. We posit that new challenges in this niche set in motion a positive feedback loop in selection pressure for cooperation that ratcheted coevolutionary changes in sociality, communication, brains, cognition, kin relations and technology, eventually resulting in egalitarian societies with suppressed competition and rapid cumulative culture. The increasing pace of information innovation and transmission became a key aspect of the evolutionary niche that enabled humans to become formidable cooperators with explosive population growth, the ability to cooperate and compete in groups of millions, and emergent social norms, e.g. private property. Despite considerable fitness interdependence, the rise of private property, in concert with population explosion and socioeconomic inequality, subverts potential transition of human groups into evolutionary entities due to resurgence of latent competition and conflict. This article is part of the theme issue 'Human socio-cultural evolution in light of evolutionary transitions'.

Scoping Review of Biological and Behavioral Effects of Babywearing on Mothers and Infants

OBJECTIVE

To synthesize the evidence on the biological and behavioral effects of babywearing on mothers and infants.

DATA SOURCES

We searched PubMed, CINAHL, Embase, PsycINFO, Sociological Abstracts, SCOPUS, and Google Scholar for peer-reviewed, full-text research articles published in English in which researchers reported on the biological or behavioral effects of babywearing on mothers or infants.

STUDY SELECTION

We reviewed the titles and abstracts of 200 records and abstracted 80 for full-text review. Of these, 29 studies met the eligibility criteria and were included in the review.

DATA EXTRACTION

We used the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR) and extracted the following data from the included articles: author(s), year of publication, setting, aim/purpose, design, description, sample, results/outcomes, and implications to practice.

DATA SYNTHESIS

We synthesized data from the included studies into the following eight themes: Increased Contact, Responsiveness, and Secure Attachment; Physiologic Effects; Biomechanics and Positioning; Facilitating and Empowering; Comfort; Maternal Benefits; Speech, Vocalizations, and Tempo; and Beliefs and Perceptions About Babywearing.

CONCLUSION

Babywearing may have a range of beneficial biological and behavioral effects on mothers and infants. The evidence, however, is insufficient to inform practice recommendations, and additional research is warranted.

Anthropo-Mechanical Cradles: A Multidisciplinary Review

Domestic cradles are beds that are movable but non-mobile for babies up to five months of age. The "anthropo-mechanical" cradle simulates the physiological movement of the human body. The article reviews scientific literature discussing the impacts of swinging on infants, provides classifications of all currently used cradles due to how the child moves, and briefly describes modern technologies within cradle automation. This made it possible to calculate and propose safe motion parameters within mechatronic cradles. The main conclusions of the article are as follows: (1) the scientific literature reports the beneficial effects of harmonic movement on a child, (2) motion analyses substantiating the classifications of all cradles into six types (tilting, yawing, hammock, Sarong, swing, and surging cradle; the classification criterion included the nature of the cradle movement in relation to the planes and anatomical axes of the child's body), (3) modern technologies allowing for the use of movement with thoughtful parameters, thus, safer for a child, (4) movement within the parameters similar to the motion and speed passively performed by the child in the womb while a mother is walking was considered beneficial and safe, and (5) the use of advanced technology allows for the possibility to devise and create an automatic mechatronic cradle with a child-safe motion. Future innovative anthropo-mechanical cradles that follow physiological human motion parameters can be used safely, with a vertical amplitude ranging from -13 to + 15 mm and a frequency of up to 2 Hz.

[The psychomotrician, mediator during the carrying process between a mother and her baby]

The carrying in the arms of the young child by his mother is necessary during breastfeeding, for example. But it also occurs during moments of cuddling. These times of bodily proximity, with no other end than the relationship and tenderness, encourage the weaving of emotional bonds between the adult and his baby. If the adjustment between the two partners goes relatively well in most cases, certain dyads present interactive difficulties and the cuddles seem less fluid, less natural. Psychomotricians can then intervene to support the partners in the interaction by playing a mediating role.

Evaluating the human capacity of carrying loads without costs: A scoping review of the Free-Ride phenomenon

OBJECTIVES

Several researchers have obtained discordant results testing the human capability to transport loads without added locomotion costs. Carrying loads has an extended relevance to human ecology, thus a review of the Free-Ride phenomenon detection according to the existing literature is needed.

METHOD

A search was made in November 2021 in SCOPUS, Google Scholar, and Web of Science to identify studies comparing the energy expenditure of loaded and unloaded locomotion. Descriptive percentages were calculated with the data obtained from each study, and a Chi-squared (χ² ) independency test and a contingency table were applied to observe the relationship between sample characteristics, experimental procedures, and the detection of the Free-Ride.

RESULTS

A total of 45 studies met the inclusion criteria. Eighty two percent do not detect the Free-Ride phenomenon. The general detection is independent of sex, experience, load position, load size, and speed (p value >.05) although the papers detecting the Free-Ride have some common characteristics.

CONCLUSION

The literature does not support a Free-Ride capacity, but future research testing this phenomenon should consider the load size, the load position, the level of expertise, or the speed. As the Free-Ride is not generalizable, it can be hypothesized that other mechanisms may have emerged during human evolution to buffer the energetic demands of load carrying.

Caregiver-child proximity as a dimension of early experience

Human infancy and early childhood is both a time of heightened brain plasticity and responsivity to the environment as well as a developmental period of dependency on caregivers for survival, nurturance, and stimulation. Across primate species and human evolutionary history, close contact between infants and caregivers is species-expected. As children develop, caregiver-child proximity patterns change as children become more autonomous. In addition to developmental changes, there is variation in caregiver-child proximity across cultures and families, with potential implications for child functioning. We propose that caregiver-child proximity is an important dimension for understanding early environments, given that interactions between children and their caregivers are a primary source of experience-dependent learning. We review approaches for operationalizing this construct (e.g., touch, physical distance) and highlight studies that illustrate how caregiver-child proximity can be measured. Drawing on the concepts proposed in dimensional models of adversity, we consider how caregiver-child proximity may contribute to our understanding of children's early experiences. Finally, we discuss future directions in caregiver-child proximity research with the goal of understanding the link between early experiences and child adaptive and maladaptive functioning.

Infant carrying is associated with reduced maternal repetitive negative thinking and increased maternal mental health

INTRODUCTION

Mental disorders, such as postnatal depression, are common in mothers. Repetitive negative thinking has been identified as a cognitive factor underlying the resulting difficulties in mother-infant interactions.

METHOD

The present online survey investigated associations between infant carrying (baby-wearing) and maternal repetitive negative thinking and positive mental health.

RESULTS

Repetitive negative thinking was significantly lower, and positive mental health was significantly higher while carrying compared to overall levels. There were no relations between maternal mental health and frequency of carrying. Maternal activities during carrying are portrayed.

CONCLUSION

These results are the first indication that carrying could be a low threshold, easily administered intervention method for maternal mental health problems.

Physical contact in parent-infant relationship and its effect on fostering a feeling of safety

The infant-caregiver relationship involves physical contact for feeding, moving, and other cares, and such contact also encourages the infant to form an attachment, an emotional bond with the caregivers. Physical contact always accompanies somatosensory perception, which is detected by mechanosensory neurons and processed in the brain. Physical contact triggers sensorimotor reflexes such as Transport Response in rodent infants, and calm human infants while being carried. Tactile sensation and deep pressure in physical interactions, such as hugging, can function as emotional communication between infant and caregiver, which can alter the behavior and mood of both the infant and caregiver. This review summarizes the findings related to physical contact between the infant and the caregiver in terms of pleasant, noxious, and neutral somatosensation and discusses how somatosensory perceptions foster a feeling of safety that is important for infant's psychosocial development.

Ticks, Hair Loss, and Non-Clinging Babies: A Novel Tick-Based Hypothesis for the Evolutionary Divergence of Humans and Chimpanzees

Human straight-legged bipedalism represents one of the earliest events in the evolutionary split between humans (Homo spp.) and chimpanzees (Pan spp.), although its selective basis is a mystery. A carrying-related hypothesis has recently been proposed in which hair loss within the hominin lineage resulted in the inability of babies to cling to their mothers, requiring mothers to walk upright to carry their babies. However, a question remains for this model: what drove the hair loss that resulted in upright walking? Observers since Darwin have suggested that hair loss in humans may represent an evolutionary strategy for defence against ticks. The aim of this review is to propose and evaluate a novel tick-based evolutionary hypothesis wherein forest fragmentation in hominin paleoenvironments created conditions that were favourable for tick proliferation, selecting for hair loss in hominins and grooming behaviour in chimpanzees as divergent anti-tick strategies. It is argued that these divergent anti-tick strategies resulted in different methods for carrying babies, driving the locomotor divergence of humans and chimpanzees.

Human Lateralization, Maternal Effects and Neurodevelopmental Disorders

In humans, behavioral laterality and hemispheric asymmetries are part of a complex biobehavioral system in which genetic factors have been repeatedly proposed as developmental determinants of both phenomena. However, no model solely based on genetic factors has proven conclusive, pushing towards the inclusion of environmental and epigenetic factors into the system. Moreover, it should be pointed out that epigenetic modulation might also account for why certain genes are expressed differently in parents and offspring. Here, we suggest the existence of a sensitive period in early postnatal development, during which the exposure to postural and motor lateral biases, expressed in interactive sensorimotor coordination with the caregiver, canalizes hemispheric lateralization in the “typical” direction. Despite newborns and infants showing their own inherent asymmetries, the canalizing effect of the interactive context owes most to adult caregivers (usually the mother), whose infant-directed lateralized behavior might have been specifically selected for as a population-level trait, functional to confer fitness to offspring. In particular, the case of the left-cradling bias (LCB; i.e., the population-level predisposition of mothers to hold their infants on the left side) represents an instance of behavioral trait exhibiting heritability along the maternal line, although no genetic investigation has been carried out so far. Recent evidence, moreover, seems to suggest that the reduction of this asymmetry is related to several unfavorable conditions, including neurodevelopmental disorders. Future studies are warranted to understand whether and how genetic and epigenetic factors affect the lateralization of early mother-infant interaction and the proneness of the offspring to neurodevelopmental disorders.