Busting myths about evolutionary biology and infant care generally
| # | Outdated idea | Updated evolutionary science |
|---|---|---|
| 1 | The "Obstetrical Dilemma" hypothesis proposes that Homo sapiens infant born most neurologically immature of all primates because of large head size and narrow bipedal pelvis. | Midwifery practice is widespread culturally and likely to be a necessary part of Homo sapiens' biocultural evolution, optimising birth outcomes in the human context where foetopelvic fit is closer than in all other primates. (This close foetopelvic fit is not pathological, but evolutionarily stable for the human in the context of midwifery support.) Grunstra et al 2023 propose it's more likely that relative neurological immaturity at birth is explained by a complexity of factors, including developmental plasticity in response to environmental factors, the metabolic demands of our large brain, and natural selection pressures upon foetopelvic fit. Gunstra et al note that evolutionary compromises in complex organisms are the rule rather than the exception (and not confined to female human bodies). An "evolutionary entanglement of biological and sociocultural factors" underlie considerations of human childbirth and risk minimisation. I propose that the same applies to lactation support, and the support of families with babies, too. |
| 2 | The "Energetics of Gestation and Growth" (EGG) hypothesis proposes that birth is initiated when fetal energy requirements exceed the mother's maximum sustained metabolic rate, around 2.1 × basal metabolic rate of the non-pregnant, non-lactating condition. | See above. |
| 3 | The infant is an exterogestate foetus for the first three months of life, giving rise to the concept of the fourth trimester. | Postnatal brain development occurs at a foetal-like for the first year or so. The exterogestation period can be thought of as nine months postbirth, up until locomotion. |
| 4 | Mothers know how to best respond to, care for, and breastfeed their infants if they tune in to their 'natural instincts' or 'intuition'. | This concept does not align with evolutionary biology, which demonstrates the fundamental and unique role of cultural heredity in the evolutionary development of Homo sapiens. Caring for an infant draws on cultural repositories of knowledge developed up over many generations, and available to contemporary mothers from family, friends, health professionals, and a wide range of other sources. It is, however, important that cultural knowledge imparted to contemporary women, and environmental factors, don't disrupt her capacity to experiment with responding to her baby (a common contemporary problem). The idea of the 'natural' is often quite unkind of mothers, who then feel 'unnatural' when they strike infant care challenges. For this reason, the idea of the natural is not used in the Possums programs. |
| 5 | Too much left brain input interrupts the natural flow of a mother's right brain as she cares for her baby. | This simplistic framing of the left and right brain is based on popular conceptions from last century. Psychiatrist and researcher Dr Iain McGilchrist has demonstrated that the left and right brain necessarily work together, though life goes best for the human when the highly verbal, categorising left brain serves the right brain, with its physically aware, integrating, scanning and feeling-sensing skills. Possums argues that contemporary women need excellent evidence-based information which is assimilated by the left brain but which strengthens the right brain's capacity to sense, respond, and enjoy through experimentation with various physical or somatic infant care practices. |
| 6 | "We're not Kung! Peoples. Unregulated breastfeeds and sleep are incompatible with the demands of paid work and contemporary Western lifestyle." | I've heard this said in various contexts over the years, demonstrating an outdated, 20th century understanding of anthropology and evolutionary biology. Researchers had demonstrated high frequencies of night waking and breastfeeding in the Kung! People communities - shown in other research as not necessarily typical of other First Nations cultures. However, in traditional contexts, in addition to infant care day and night, women often played demanding roles in service of community and family, occupations which required high levels of attentiveness, alertness, and intellectual acuity if she was to protect loved ones and other community members from injury and danger. |
| 7 | Parents need to regulate the biology of infant feeds and sleep using clock-based methods and graduated extinction methods, in order to make life as manageable as possible now, and to create good habits which will optimise the child's future development, independence, and wellbeing. This myth came to the fore in the 1950s, and has been a part of last century's scientification of parenting (often referred to as Scientific Motherhood). | This is not an evolutionarily aligned belief. It has been the standard Western approach for asserting control over the stress and distress that arise from feeding, sleep and cry-fuss problems (in the absence of effective clinical interventions). From an evolutionary perspective, biobehavioural synchrony across these domains between mother and baby, parent and infant, optimises mental health and wellbeing for parents, and optimises developmental outcomes. |
Recommended resources
Evolutionary biology basics for health professionals who work with parents and infants
Breastfeeding durations in ancestral environments. A little extra something - part 3
Busting myths about evolutionary biology and breastfeeding
A timeline of relevant evolutionary events for health professionals who care for parents and infants