Review of Melvin Konner’s The Evolution of Childhood: Relationships, Emotion, Mind (Harvard University Press, 2010)
KeywordsEvolution Childhood Biobehavioral development Foragers
This massive book (750 pages of text and another 150 pages of references) is a comprehensive, integrative treatment of what is known about human childhood and how to think about it from an evolutionary perspective. It is a landmark reference book, suitable for use by a grad student or scholar, and usable in a graduate seminar, but the book’s length and density precludes it being very useful in lower-level classes, and many audiences unfamiliar with aspects it covers will find the terminology and going dense.
It feels like a real investment to read and engage such a volume in the day and age of the tweet, not to mention short scientific articles and books. For serious students of childhood, however, reading the book is well worth the investment of time. The author not only gives a clear overview of what he and others have learned about childhood over his long career, he provides an integrative organizing framework that helps to distinguish what we know about childhood from what we can have the tools to investigate. In that sense, this volume is as much a blueprint for future work as a synthesis of past and present findings.
Human childhood is a topic of great interest to a variety of disciplines, including psychology, biology, pediatrics and social work, the practitioners of which are all potential readers of Human Nature. The tip-off that this book is written by an anthropologist comes from its organization into four sections: evolution, maturation, socialization, and enculturation. Konner makes it clear that although all species mature and many are socialized during childhood, humans are perhaps the only species whose childhood also involves enculturation. It is a nifty way to include humans within the spectrum of animal continuity yet point to a feature of humans that requires its own set of definitions and analyses.
There is no way I can do justice to this book in a single essay. Its multitude of themes, countless examples, and overarching integrative structure defy simple characterization. So I have chosen to highlight the points that I found particularly interesting, provocative, or noteworthy. And because it has been the development of an evolutionary perspective that marks the intellectual arc of Konner’s own work, I have given that which is evolutionarily salient the most attention, at the expense of providing even coverage of the entire book.
In fact, Konner’s title does not distinguish between biological and cultural evolution. Yet his integrative model with its nine levels of causation/explanation helps to clarify the analytic separation between phylogenetic and cultural elements in the evolution of childhood. These two aspects of childhood are like an interlocking set of Chinese rings: loosely linked together but clearly separable into two more tightly linked sets. The biological processes of maturation are interconnected by a network of physiological mechanisms that link the body and brain; similarly the processes of ecology, economy, and social organization constitute a web of connections linking individuals within cultures. The tremendous variation we observe in cultural practices can only impinge on the much more limited variation possible in the biology of childhood development at specific intersections.
So it is productive to separate questions about the evolutionary heritage of human childhood from those about the degree of observable cultural variation in childhood development. The evolutionary questions consider the biological mechanisms that result in the basic human pattern of childhood development and their adaptive basis. This section of the book also compares these patterns with those of our closest relatives (whether living or fossil) to determine how child development has changed over our evolutionary history, and how such changes represent alteration in the larger context of human social capacity. This section also focuses on hunter-gatherers as the critical social context of human childhood development.
Evolution: The Phylogenetic Origins of Childhood
The first section of the book outlines the evolutionary processes and principles relevant to human childhood. For his evolutionary framework, Konner expands Tinbergen’s well-known four levels of biological explanation (evolution, adaptation, development, and causation) to nine levels and argues that without any one of them an explanation of human childhood (or any other human trait) is not complete. Konner’s nine levels of analysis are phylogenetic constraints, ecological/demographic causes, and the genome, under the heading “Remote or Evolutionary Causation”; embyronic/maturational processes, formative early-environment effects, and ongoing environmental effects, under the heading “Intermediate or Developmental Causation”; and finally under “Proximate or Functional Causation,” longer-term physiology, short-term physiology, and elicitors or releasers.
There is little here that will be particularly new to readers of Human Nature. Some may argue with Konner’s nine levels of explanation or his choice of specific levels, but the structure provided by this outline is useful for drawing attention to the gaps in our understanding of human childhood without having to call into question the value of what we do already know. This is one of the most satisfying aspects of the book; in a world where reductionist answers are the default, it demands that the reader keep an open mind about all that may be necessary as an adequate framework for understanding the evolution of childhood.
The first section is also worth reading for the way in which Konner summarizes so many of the interesting developments in behavioral biology over the past 70 years. I found the section on ethology particularly important. It is the sort of summary that today’s graduate students need to read if they want to understand the development of evolutionary anthropology. Today the idea of evolutionary structure to the brain and behavior is widely if not universally accepted. Our current understanding has moved beyond the simpler idea of fixed action patterns and innate releasers. However, when I was a student the dominant paradigm was still behaviorism, in which animals were regarded as automatons devoid of feeling and thought. It was a matter of belief, as for so many indigenous societies, that animals are social, communicative, and intentional, and that they were on a spectrum with humans in terms of possessing some sort of a mind. Ethology supported that belief for a long time when it was not the mainstream academic opinion in the United States.
The other evolutionary section that deserves special comment concerns life history theory as a critical part of understanding human life stages. Life history theory is evolutionary developmental biology (“evo-devo”) on an organismal level, with childhood as a central focus. On page 143 Konner notes that “the future of Evo-Devo belongs to genetics,” a sentiment with which I agree. Not only are genetic and epigenetic techniques a powerful way of understanding development in living organisms, but with ancient DNA, such techniques can also be applied to questions about human evolutionary history to which the bones themselves can’t speak.
But if the future of evo-devo belongs to genetics, the present belongs to life history. Life history has the capacity to take the expression of a wide range of behaviors over the life course and bring them together to show how as a whole they change in frequency and importance during different life stages, not to mention assessing how they trade off against future costs and benefits. Without this larger perspective, it is difficult to define phenotypic traits that can be investigated at the genetic level.
Two examples provide a telling illustration of the current gap between the power of life history theory and that of genetics to illuminate the evolutionary underpinnings of childhood. In the first, Konner brings up the so-called fourth trimester (p. 206), the first 3 months of life, in which the infant shows relatively few signs of initiating social interaction. The idea of the fourth trimester was novel to me. Konner argues that during this very early stage of life mortality risk is still high and the mother is not yet fully attached to an infant who still has a reasonable chance of not surviving.
This contrasts with the more general understanding that mother/infant bonding begins at birth. Presumably, the mother’s positive orientation toward the baby starts at birth, but actual attachment requires the infant to elicit an emotional response from the mother. The strength of the mother’s response varies, depending on the strength with which it is elicited by the infant’s behavior. It’s a good example of how two different elements of a simple system can be summed to achieve a more flexible trade-off. Konner explores this issue in some detail in a discussion of Nancy Shepard-Hughes’s much-debated book Death without Weeping to illustrate that while maternal investment may be contingent on the infant’s chances for survival, maternal sentiment is not.
Konner’s summary of material on genes and development is interesting, but few of the results from species other than humans seem directly relevant to understanding the development of human behavior. Konner discusses homeobox genes which underlie variation in the highly conserved body plan of vertebrates, perhaps the most ubiquitous illustration of evolutionary developmental (evo-devo) genetics. It’s a wonderful example of the overarching power of an evo-devo approach to explain the commonality among far-flung species. It is also an example that seems to have little direct relevance to the development of behavior over the course of human childhood.
Over the past 10 years, however, an example of how genes might directly impact child development at a level that is both demonstrable and intuitively meaningful has emerged. This is the role of the DRD4 dopamine receptor on the behavior of young children in response to parenting. Children with the 7R+ allele show a greater impact on their behavior, both negative and positive, of supportive parenting (see Bakermans-Kranenburg and van IJzendoorn 2011 for a recent example). This effect of the 7R+ allele has now been demonstrated not only among infants, but among early teens as well (Marsman et al. 2013). Dopamine transmission underlies the reward system, and variation in dopamine receptors alters neural sensitivity to dopamine. Thus it appears that children who are genetically more sensitive to reward are more likely to be responsive to, and hence shaped by, parental behavior than those who are not so genetically inclined. The implications of such an intimate and enduring gene-environment interaction on parenting, not to mention the role of culture through its effects on parental behavior, in shaping childhood are intriguing.
But as I suggested earlier, we can describe relatively few such evo-devo threads at the genetic level, nor have their phenotypic effects been put together in a coherent picture on their own. It is still the pattern of development at the organismal level—in other words, life history—that is most instructive at this point in time. For instance, Konner’s comparison of apes and humans documents the following changes in development timing: increased life span and time to sexual maturity, slightly longer gestation, prolongation of rapid brain growth with suppression of bodily growth leading to juvenilization of some anatomical and behavioral features, along with the insertion of a new developmental period—middle childhood—between infancy and puberty.
I believe that this last point reflects a blurring of timing and function. To my way of thinking, it is early childhood, not middle childhood, that is novel in the human life cycle. Middle childhood in humans corresponds to the juvenile stage in apes, which extends from weaning to the onset of puberty. But unlike in apes, in humans the same period between weaning and puberty contains within it two separate stages; early childhood and middle childhood. Early childhood is defined from weaning to adrenarche and middle childhood from adrenarche to puberty. Of the two, early childhood is the novel phase based on the comparison of weaning times between chimpanzees and humans. In chimps, individuals depend on their mothers until about 5 years of age and at that point become semi-self-sufficient. Human hunter-gatherers, on the other hand, exhibit weaning around the age of 3 years. Yet based on variation across species, mammals of our brain size would be expected to wean at about 7 years of age.
Thus, the period between 3 and 7 years of age, during which offspring are no longer wholly dependent on mom but are still not entirely on their own, stands out as unusual in humans. The shortening of the period of maternal energetic investment is made possible by the nutritional and child care contributions of others, including males and female kin. In early childhood the focus of investment broadens from mom to include the rest of the family. At the same time, middle childhood, though not a new life phase in humans, does take on a new function. It represents the period during which the individual gains a measure of self-sufficiency and social autonomy and the human brain becomes mature enough for enculturation, a point I will return to later.
Evolutionary changes in the stage of human development might be expected to show up in the human fossil record, as Konner discusses. Unfortunately, there is only very limited fossil evidence from which development can be inferred throughout most of hominid history. This is reflected in the naming of the best-known fossil juveniles, such as the Taung Child, the Turkana Boy, Lucy’s Child. It is not until Neanderthals that there is sufficient number of juvenile specimens to attempt analysis of growth patterns, such as Gunz et al.’s (2012) recent comparison of shapes changes in human versus Neanderthal skulls.
Konner ends the evolutionary section with a focus on different paradigms for the basis of psychosocial function in the brain. These include the limbic system model, the orbital frontal cortex and somatic marker hypothesis, the polyvagal model, and lateralized emotional functions. There is not room here to discuss the different models, but anthropologists interested in the evolution of childhood should become familiar with them as conceptual tools for simplifying and making tractable the emotional systems of the brain and their implication for the patterning of childhood behavior.
Maturation: Anatomical Bases of Psychosocial Growth
In keeping with Konner’s focus on brain evolution at the end of the previous section, we are learning that much of human behavioral development is maturational—in other words, that it is not dependent on learning or the environment, but simply a function of the brain’s own unfolding developmental program. This is biobehavioral development; as the brain develops physically (read physiologically and anatomically), so too do its information-processing capacities, and their behavioral expression. Konner does a good job of making the maturational processes of early child development clear. Myelination of the motor tracts underlies the development of walking, and given the characteristic timing of language acquisition, myelination play a key role in its developmental timing as well. These well-known examples underlie the adage “Walking by one, talking by two.” It is a reliable pattern because it depends on brain maturation rather than environmental experience. Attachment, as the most basic form of socialization, is also a maturational process, as discussed earlier with regard to the fourth trimester.
The fact that human children are talking at about the age that they are being weaning in hunter-gatherer societies is really rather mind boggling, given that our cultural pattern of breastfeeding has separated the timing of language acquisition and weaning. But it makes a lot of sense that as the child moves away from such a strong dependence on mom, with whom it shares both genetic similarity and bodily communication, it is able to communicate vocally with others. Interestingly, the emergence of self-reflectivity around the age of 1½ to 2 years (Lewis and Ramsay 2004) appears to precede the development of language and weaning. Freud may have gotten something right: For almost 3 years, the infant’s development, including self-awareness, is indeed tied to mom as its most salient social context.
The milestones of infancy and early childhood are not the only traits tied to the process of brain maturation. So too are aspects of social behavior, emotions and cognition more broadly, that start to emerge predictably during Piaget’s “5 to 7 transition.” It is during this period that different areas of the cortex begin a process of sequential hierarchical myelination, leading to greater integration between brain regions (Gogtay et al. 2004) and the capacity for more complex behavior. It is also at this point that that there is a net loss of synaptic connections within the cortex—in other words, only those synaptic connections that are repeatedly reinforced by use are retained, making cultural practices all that more influential in shaping behavioral outcomes.
Thus, as far as I can tell, Konner misses a point when he says that early brain development is experience-dependent without specifying the parts of the brain to which he is referring. Subcortical structures associated with emotion and memory, such as the amygdala or hippocampus, that develop during infancy and early childhood are undoubtedly shaped by experience during that period (see Luby et al. 2013 for an example). But it is only around the age of 8 that the cortical structures that cognitively appraise the emotional information from such subcortical structure start to loss their plasticity. This may be what Konner is thinking of later in the book when he says that early childhood experience has few, if any, lasting effects. We will return to this point later.
As Konner discusses, the middle childhood transition marks a shift in social context from the family toward peers. Children initiate greater distance from their parents, and relationships with peers become more important. These changes are often overlooked because of the prominence of puberty, yet they seem to happen around the same time across cultures (Lancy and Grove 2011), suggesting that they represent a maturational process. In addition, although middle childhood is not associated with the development of either secondary sexual characteristics or sexual behavior, important gender differences start to emerge during this period, including increased modesty in clothing (Grove and Lancy 2014).
As Konner discusses, the behavioral changes of middle childhood are associated with characteristic somatic changes, including the obesity rebound, dental eruption patterns, and changes in limb proportions, thus demarcating a new stage of child development. In addition, the onset of middle childhood is marked by a rise in the adrenal production of dehydroepiandrosterone (DHEA), a process referred to as adrenarche (see Campbell 2011 for a recent review). Only very recently has it been demonstrated that DHEA is in fact associated with human brain development. Cortical thickness in prefrontal and parietal regions of the brain has been related to variation in DHEA levels between the ages of 3 to 11 years (Nguyen et al. 2013). Importantly, development of the parietal area has been associated with mentalization and a sense of self (Gweon et al. 2012; Saxe et al. 2009). Thus middle childhood is the point at which the development of the brain, a maturational process, goes beyond socialization and gives rise to the uniquely human enculturation process discussed in the next section.
In terms of maturation, adolescence has received much more attention than middle childhood, in large part because the secondary sexual characteristics that emerge with puberty are meant to draw social attention. The physical changes in adolescents, including the development of secondary sexual characteristics, are so noticeable that they can’t be ignored by either peers or parents. The behavioral changes during adolescence are equally dramatic, especially when compared with the behavior of adults.
The adolescence transition is not a simple adoption of adult behaviors. It is the adoption of behaviors that are directed toward peers as opposed to those directed toward adults. Adolescents are motivated by different things than adults. For instance, Steinberg (2008) has shown that cognitive development, as measured by working memory, digit span, and verbal fluency, appears to be more or less gradual between the ages of 10 and 30 years. But psychosocial maturation, as measured by impulsivity, risk perception, sensation-seeking, future orientation, and resistance to peer pressure, seems to lag behind until about 18–20 years of age and then increases rapidly toward adult levels.
The fact that the prefrontal cortex, the last part of the brain to mature, continues to develop into the twenties means that the overall change in adolescent behavior is maturational. Adolescent brains are particularly susceptible to peers and the opposite sex during this period. These social influences will play a large role in shaping the brain during this stage. In other words, the process of maturation presupposes a certain social environment, one that leads to a range of expected outcomes. This is the basis of socialization, Konner’s third level.
But before I move on to discussing socialization I would like to pick up on the possible impact of testosterone in the male brain on the development of empathy (Chapman et al. 2006), a point that Konner raises but does not pursue. More recent brain imaging results have substantiated the mechanism, showing that testosterone alters connections between the amygdala and the orbital frontal cortex both prenatally (Lombardo et al. 2012) and postnatally (Mehta and Beer 2010), at the same time increasing those in the parietal lobe. In other words, it appears that sex hormones do play a role in sex differences in human brain maturation.
Socialization: The Evolving Social Context of Ontogeny
Given that the maturation patterns of childhood are a product of evolution, the social context of species-typical human development at the organismal level is the hunter-gatherer lifestyle. Hunter-gatherers are generally described as small-scale, kin-based groups with face-to-face social interactions. But for the child the meaningful social context can be characterized more specifically as it expands over the course of childhood. For infants the social context is highly centered on mom; during early childhood, other family members become increasingly salient, followed by children from same and other families in middle childhood and finally members of other groups during adolescence.
The original studies of the !Kung by Konner and others provided evidence for the primacy of the mother in infant care, reinforcing in the minds of many the importance of mothers in our own culture. But how representative are the !Kung in terms of hunter-gatherers generally? As more fine-grained data have come in over the past 50 years, it has become clear that ecological conditions and social practices vary across hunter-gatherers (Kelly 2013). Patterns of mother-infant interaction may vary as well, but given the essential nature of breastfeeding such differences are likely to be more highly constrained.
Konner takes up this question in his discussion of the hunter-gatherer childhood (HGC) model that he derived from his work with the !Kung. The HGC suggests that infant time is spent with mom. He compares the HGC to the facultative childhood adjustment model (FCA) proposed by researchers who have worked with other groups, including the Hadza, the Agta, the Ache, and the Aka. The key question is the amount of time the infant spends with the mother vs. other relatives, including fathers and grandmothers.
Considering the available data, Konner finds relatively little difference in the amount of time that infants spend with mom between the five hunter-gatherer groups. In all the groups, including the Aka, among whom fathers spend much more time with infants than fathers in the U.S., mothers spend far and away the most time with the infant. Infants also spend the majority of time with mothers among the Agta despite the fact that women hunt more than in the other hunter-gatherer groups.
Indeed the data from the Aka point to differences in how mothers and father spend time with their infants and very young children. Konner points out that Aka mothers spend the majority of their time with the infant feeding and transporting it, whereas fathers spend more of their time with the infant hugging, kissing, or cleaning it. In addition, more of the father’s time is spent in educating children. These differences are echoed in a recent study which found that mothers and fathers of an infant show similar levels of oxytocin, but among mothers oxytocin was associated with affectionate parenting behaviors, including “motherese” vocalizations, the expression of positive affect, and affectionate touch, whereas among fathers oxytocin was related to stimulatory parenting behaviors, including proprioceptive contact, tactile stimulation, and object presentation (Gordon et al. 2010).
Just as nursing is a constraint that makes mom the center of the infant’s social context, the demography of hunter-gatherer groups is a key constraint in the social context of early and middle childhood. Given the small size of hunter-gatherer bands today and presumably in the past, there are always a limited number of children at any one time. Thus, once children can be left to their own devices, they are part of a child-centric mixed-age group. This social context lends itself to the development of play as a mode of social learning. It features cooperation among individuals with different levels of ability rather than competition among more or less equally matched individuals. These conditions reinforce elements of play, including turn-taking, role reversal, and lack of an ultimate goal. These behavioral features are also important among adults, where individual autonomy is critical to all collective endeavors. In fact, Peter Gray (2009) characterizes the nature of hunter-gatherers’ social organization as “play,” and Thomas Malby (2009) suggests that play remains a part of our nature in the modern world as an essential “disposition” for adults as well as children.
For adolescents, the small size of hunter-gatherer groups leads to a different outcome in terms of socialization. Boys who can now provide their own subsistence spend much of their time visiting other groups in order to find girls. They also develop working relationships with older males. Girls, on the other hand, spend much of their time flirting with boys, even while performing women’s subsistence tasks. Not surprisingly, as Konner recounts, there is a fair amount of sexual activity among adolescents in hunter-gatherer groups.
At the same time, Konner emphasizes that interactions with the opposite sex are not just about sex but also include affection and romance. In other words, the social context of adolescence is not sexual partners, but pair bonding or attachment. Konner makes the observation that romantic love often takes on the shape of an adolescent tantrum, as much about rebellion against parental attachment as it is about forming a new attachment. This promising insight highlights the importance of attachment in the adolescent transition. Unfortunately, Konner does not elaborate on it.
Enculturation: The Transmission and Evolution of Culture
“Culture” is one of those terms we all use, but which lacks a clear common definition. I have come to favor the idea of culture as shared mental representation. What mental representations are shared must be learned—in other words, culturally transmitted. As I mentioned earlier it appears that it is not until the age of 6 or 7 years that children are capable of complete mental representation. So it is at this point that kids start being enculturated—in other words, learning the locally shared cultural representations.
Lancy and Grove (2011) have pointed out that in many traditional societies infants and toddlers are considered to be stupid, to lack common sense, and to be incapable of learning. Parents, busy with any number of subsistence tasks, are concerned about providing for the infants’ basic needs but do not have time to instruct them. It is only when children reach the age of 6 or 7 years that children become “educable” and are given instruction. Children are taught (and here learning is done by a mix of instruction, observation, and play) subsistence tasks in preparation for becoming competent adults, because cultural knowledge will enable them to make a living in the same environments their parents experienced. Such tasks require not only trained skills, but the social and emotional maturity to interact with others and ensure that the tasks are carried to completion.
On the other hand, in industrialized societies parents are not as directly consumed with subsistence tasks and children may eventually earn their living doing something very different from their parents. So the focus is on general tasks, such as learning to read and write, that can be taught before the maturity needed to perform socially useful tasks outside the home is acquired. Thus there is increasing pressure to teach children skills at ages before they can fully master their use. In the suburban culture this pressure focuses primarily on mothers, adding another layer to the maternal myth.
If enculturation adds shared mental representations as the newest layer in human development, the learning process does not stop with middle childhood but continues into adolescence. While younger children are learning to play by the social rules, most of them given by adults, adolescents are learning to play with the social rules as young adults. Thus adolescence may be characterized as a period of innovation in which individuals try out new variants of established practices. This is interesting to consider in terms of the very late appearance of innovation in the archaeological record of human evolution and may tell us something about when adolescence became an established phase of human life history (Kyriacou and Bruner 2011).
Any questions I may have had with Konner’s presentation of childhood up to this point are quibbles. But I found myself disagreeing with his emphasis with regard to the impact of childhood stress and adversity on later development. At the beginning of Chapter 14 (p. 363) Konner states that there is little firm evidence for the impact of early childhood on later development. Konner elaborates this point on pages 610–611, where he discounts the experience of psychodynamic clinicians in describing the impact of early childhood experience because retrospective interviews are not persuasive.
But Konner’s concern goes deeper than the old antagonism that many scientists seem to have toward Freud. Konner also discounts prospective studies by developmentalists because “without random assignment or genetic controls the correlations can be otherwise explained” (p. 611). He makes his point emphatically: “the fact remains that developmental psychologists, psychodynamic psychiatrists and other psychotherapists and educational researchers of many theoretical and methodological persuasions have failed to show to the satisfaction of reasonable skeptics that decisive, lasting effects of early experience in the normal range exist, much less how such effects might work” (p. 611).
This puts a different slant on Konner’s discussion of stress during childhood in Chapter 21, where he emphasizes the high degree of resilience to childhood adversity, whether from physical abuse, emotional neglect, sexual abuse, life on the street, or war. Konner of course recognizes that responses to the same childhood stress vary across individuals. He arranges them on a continuum with three gradations: (1) those who become sensation seekers as a result of acute stress; (2) those who respond to trauma with acute dis(stress) that often fades with time; and (3) those with preexisting susceptibilities that make them vulnerable to psychiatric illness during and after trauma. Konner suggests that the vast majority of children fall into the middle category.
My beef is not with Konner’s assertion that most children are resilient, but with the fact that his caveats lead to such a narrow window of conditions for the effects of early experience as to be almost meaningless. They seem to ignore John Bowlby’s classic work on attachment and all the research it inspired. Still, Konner may have a point, so let’s go through the caveats one at a time.
Recent studies of childhood experience and subsequent depression have clearly controlled for genetic variation in a small set of genes related to brain functioning (see Aguilera et al. 2009 for one example). In general these studies find that childhood trauma increases the risk of adult depression, but the magnitude of the response is contingent on allelic genetic variation. Furthermore, two recent prospective studies suggest that early childhood neglect and abuse leads to poorer emotional functioning in middle age (Nikulina and Widom 2013; Young and Widom 2014), documenting the lasting effects of early experience. Whether early experience is decisive is less clear, given that abuse and neglect often continue into the rest of childhood.
Since random assignment of children to traumatic conditions is not ethical, we are left with the question of what defines the normal range of childhood stress. Is it the normal range of individual responses as defined by genetic variation? Or is it the normal range of childhood environments? Is a normal environment one without a single traumatic event, or without on-going stress? And are any of the childhood environments in the developed world normal or are they all WEIRD (white, educated industrialized, rich, democratic), to use the phrase coined by Henrich et al. (2010)?
We might agree that war and sexual abuse are outside the normal range, if only for the sake of not being distracted by their horrors for the moment. Emotional deprivation and/or emotional abuse do not seem to be outside of the normal range in the modern world. For instance, a recent nationally representative survey in Britain reported levels of childhood maltreatment as high as 16% (May-Chahal and Cawson 2005). That leaves us with two questions from Konner’s quote (reproduced above). How widespread is childhood trauma (in whatever form) among hunter-gatherers? And what is the mechanism by which childhood trauma affects later development?
Obviously these questions are much too complex to address in any detail here. But, they can be framed by what we already know about attachment. Hunter-gatherer cultures that do not protect young children by prioritizing the emotional well-being of the mother will produce children with predictable emotional disturbances. Events that push the mother outside of her physical and emotional comfort zone will direct her emotional attention away from the child. As long as the disruption of emotional attention is neither too severe nor prolonged the child may learn how to reengage the mother’s attention and in the process develop its own emotional resources, along with its resilience. However, any disruption of mother’s attention that the infant cannot remedy through its own actions will impair the infant’s developing emotional resources. In the case of depression, reduced emotional resources will lead to a greater risk of depression later in life when the individual is exposed to adversity.
I think that the developmental psychologists, psychodynamic psychiatrists and other psychotherapists, and educational researchers have already contributed much to our understanding of these emotional mechanisms. It will take anthropologists, neuroscientists, and others to provide their physiological and neural correlates.
With such a broad purview on childhood, Konner does not come to any single conclusion—not that one would expect him to. He did not set out to answer a specific question, but to systematize our understanding of childhood across many cultures, using evolutionary theory, brain development, life history, and anthropology, to name a few of the fields he touches on. In other words, the mode of the book is consilience, not discovery, and certainly not reductionism.
Thus, one of the great strengths of Konner’s book is its inclusiveness. His vision of childhood development integrates what are often treated as separate elements of childhood: somatic growth, emotional development, social relationships, and the mind, including culture. Without belaboring the point, he even includes the acquisition of religious beliefs as an organic part of childhood development.
Konner’s approach builds up the different layers that contribute to our understanding of childhood development until we can see a more or less complete picture of how they come together or may in the future come together. It is not a matter of the importance of maturation vs. socialization or enculturation, but how variation in each layer builds on and at the same time constrains the variation in the other layers. This is the evo-devo perspective, whether at a molecular, cellular, organ system, or organismal level. I look forward to seeing its increasing application to human childhood in the future.
- Aguilera, M., Arias, B., Wichers, M., Barrantes-Vidal, N., Moya, J., Villa, H., van Os, J., Ibáñez, M. I., Ruipérez, M. A., Ortet, G., & Fañanás, L. (2009). Early adversity and 5-HTT/BDNF genes: new evidence of gene-environment interactions on depressive symptoms in a general population. Psychological Medicine, 39, 1425–1432.CrossRefGoogle Scholar
- Gogtay, N., Giedd, J. N., Lusk, L., Hayashi, K. M., Greenstein, D., Vaituzis, A. C., Nugent, T. F., 3rd, Herman, D. H., Clasen, L. S., Toga, A. W., Rapoport, J. L., & Thompson, P. M. (2004). Dynamic mapping of human cortical development during childhood through early adulthood. Proceedings of the National Academy of Sciences of the United States of America, 101, 8174–8179.CrossRefGoogle Scholar
- Gray, P. (2009). Play as a foundation for hunter-gatherer social existence. American Journal of Play, 3, 476–522.Google Scholar
- Grove, A, & Lancy, D. (2014). Cultural variation in life phases. In J. D. Wright (Ed.), International Encyclopedia of Social and Behavioral Sciences (2nd ed.). Elsevier. (in press).Google Scholar
- Gunz, P., Neubauer, S., Golovanova, L., Doronichev, V., Maureille, B., & Hublin, J. J. (2012). A uniquely modern human pattern of endocranial development. Insights from a new cranial reconstruction of the Neandertal newborn from Mezmaiskaya. Journal of Human Evolution, 62, 300–313.CrossRefGoogle Scholar
- Kelly, R. (2013). The foraging spectrum (2nd ed.). Cambridge: Cambridge University Press.Google Scholar
- Kyriacou, A., & Bruner, E. (2011). Brain evolution, innovation, and endocranial variations in fossil hominids. Paleo Anthropology, 2011, 130–143.Google Scholar
- Marsman, R., Oldehinkel, A. J., Ormel, J., & Buitelaar, J. K. (2013). The dopamine receptor D4 gene and familial loading interact with perceived parenting in predicting externalizing behavior problems in early adolescence: the TRacking Adolescents’ Individual Lives Survey (TRAILS). Psychiatry Research, 209(1), 66–73.CrossRefGoogle Scholar
- Young, J. C., Widom, C. S. (2014). Long-term effects of child abuse and neglect on emotion processing in adulthood. Child Abuse and Neglect. doi:10.1016/j.chiabu.2014.03.008.