What is the expected human childhood? Insights from evolutionary anthropology

Abstract

In psychological research, there are often assumptions about the conditions that children expect to encounter during their development. These assumptions shape prevailing ideas about the experiences that children are capable of adjusting to, and whether their responses are viewed as impairments or adaptations. Specifically, the expected childhood is often depicted as nurturing and safe, and characterized by high levels of caregiver investment. Here, we synthesize evidence from history, anthropology, and primatology to challenge this view. We integrate the findings of systematic reviews, meta-analyses, and cross-cultural investigations on three forms of threat (infanticide, violent conflict, and predation) and three forms of deprivation (social, cognitive, and nutritional) that children have faced throughout human evolution. Our results show that mean levels of threat and deprivation were higher than is typical in industrialized societies, and that our species has experienced much variation in the levels of these adversities across space and time. These conditions likely favored a high degree of phenotypic plasticity, or the ability to tailor development to different conditions. This body of evidence has implications for recognizing developmental adaptations to adversity, for cultural variation in responses to adverse experiences, and for definitions of adversity and deprivation as deviation from the expected human childhood.

Testing the empirical integration of threat-deprivation and harshness-unpredictability dimensional models of adversity

“…It was not surprising that the dimensions themselves proved related to one another. Recall that levels of deprivation, threatharshness and unpredictability were positively associated with each other, consistent with results of other investigators (Dong et al, 2004;Green et al, 2010;Frankenhuis & Dorsa, 2021;McLaughlin et al, 2020). Despite this, there would seem to be reasons to wonder whether there could be ecological niches in which the positive associations detected herein among the three latent adversity constructs might prove to be weakeror even stronger.…”

Why and how does early adversity influence development? Toward an integrated model of dimensions of environmental experience

“…In addition to harm imposed by other agents, insufficient environmental inputs (material, energetic, or social) was another important source of harshness over human evolutionary history (Frankenhuis & Amir, 2021). In this section, we focus on the adaptive problem of insufficient environmental inputsa distinct set of selection pressures posed by the environmentand how developmental systems evolved to detect and respond to cues indicating the presence of this adaptive problem (Figure 1).…”

“…The quantity and quality of interactions with caregivers contributes to early childhood experiences of deprivation. In traditional human societies, and by inference over human evolutionary history, some caregiver-mediated forms of deprivation (e.g., early weaning, low provisioning of food, low sleeping proximity to infants, reduced carrying of children, and caregiver neglect) increase childhood morbidity-mortality risk from causes such as malnutrition, disease, physical exposure, predation, and conspecific violence (Frankenhuis & Amir, 2021;Quinlan, 2007;Volk & Atkinson, 2008. For example, in traditional human societies, maternal mortality has catastrophic and universally negative effects on the survival of young children prior to weaning age (Sear & Mace, 2008).…”

“…As discussed earlier, extrinsic morbidity-mortality, or harshness, refers to external sources of disability and death that cannot generally be attenuated or prevented. Over human evolutionary history, experiences involving harm imposed by other agents were an important source of extrinsic morbidity-mortality for children (Frankenhuis & Amir, 2021). In this section, we focus on the adaptive problem of physical harm from other agentsa distinct selection pressure posed by the environmentand how developmental systems evolved to detect and respond to cues indicating the presence of this adaptive problem.…”

“…Indeed, almost half of children in hunter-gatherer societies (the best model for human demographics before the agricultural revolution) die before reaching adulthood (e.g., Kaplan & Lancaster, 2003;Volk & Atkinson, 2013), making childhoodthe time of the human life cycle when the force of selection is the strongest (Jones, 2009;Volk & Atkinson, 2008)an intensive window for natural selection to operate on biobehavioral adaptations to stress. From an evolutionary-developmental perspective, therefore, early adversity should not so much impair biobehavioral systems as direct or regulate them toward patterns of functioning that, even if costly, are adaptive under stressful conditions (Belsky et al, 1991;Ellis & Del Giudice, 2014, 2019Frankenhuis & Amir, 2021).…”