Children, Childhood, and Development in Evolutionary Perspective
Read the article by Bjorklund and Ellis here.
Evolutionary development (evo devo) focuses on the adaptiveness of childhood rather than treating childhoods as merely an incomplete adult phase. Too often do we assume that things that we find detestable are universal defects of childhood rather than the natural adaptation to the environment predicted by childhood experience. And what childhood behaviors improve chances of survival? How do we understand the undeveloped nervous systems of infant, curious and egocentric behaviors of young kids, and the rebelliousness of adolescents.
“We propose that an evolutionary perspective can serve as a metatheory for developmental psychology — an overarching perspective that examines the distal and functional causes of behavior — which must be integrated with other more proximal causal explanations. As a metatheory, an evolutionary perspective organizes known facts parsimoniously, provides guidance to important domains, leads to new predictions, and unifies psychology with the life sciences.”
To start off, two major types of adaptations specific to development are discussed in this article.
“Some adaptations serve to benefit the organism immediately but disappear when they are no longer needed (ontogenetic adaptations), whereas others serve to prepare infants and children for life an adult (in addition to life as children — deferred adaptations).”
In evolutionary development there are at least these two mechanisms that explain childhood. A group of adaptations (ontogenetic) that helps the child deal with the problems of childhood, particularly surviving it, but can go away one those problems are no longer relevant. The umbilical cord is an oft used example.
Some adaptations (deferred) are as predictors for the future. The undifferentiated personality of childhood is a great ground of potential to take stock of what the environment is like without having survival be threatened by taking too much time to learn. This helps the adult have behavior programs that use a strategy developed from the experience of childhood.
Both of these types of adaptation work together synergistically. To adapt to diverse environments, one needs to have an open mind, and to have an open (or not fully developed) mind, one needs temporary protection from the harsh world.
Nature and Nurture
Evo devo has a lot to contribute to the classic debate of nature versus nurture. Essentially the idea evo devo adds is that genes and biology provide the potential or sensitivity to react to the environment, and the strategy patterns that result. Genetic differences can account for greater sensitivity or susceptibility towards some traits, but they always require the context in which to be created.
“From [the developmental systems theory] perspective, there are no genes ‘‘for’’ a specific trait, and genes are not granted a privileged role in development but are viewed as one integral part of the developmental system that requires input from and interaction with other components of the system to function properly. Thus, the interaction between genes and environment over development jointly contribute to the emergence of phenotypic characteristics.”
Even what we consider “preformed” instincts require an environmental and biological context in which they can be expressed. The famous imprinting phenomenon documented by Konrad Lorenz showed recently hatched ducklings instinctively follow their mother. Though it seems to be automatic, this behavior requires environmental inputs (sounds of the mother’s call) while the chicks are still in their eggs. Genes remain unexpressed without their initiating stimulus. “Normal” behavior requires species-typical environmental patterning. This can be as biological as the conditions of the womb, or as behavioral as how we hold and interact with babies.
We inherit preferences towards this normal place that scientists call the “ontogenetic niche, which is defined as the set of ecological and social factors that are reliably inherited by members of a given species.””
“Presumably, early sensory stimulation serves to organize the young organism toward certain, usually adaptive outcomes; but when sensory experience is withheld, received earlier than is normative, or experienced in excess of species-typical levels, species-atypical patterns of development result.”
Without the species-typical sensory stimulation, the organization and ordering of the nervous system will be unable to make meaning out of complex information and animals will have anxiety because their pathway for dealing with these stimuli are unformed. Yet childhood is the adaptive mechanism for putting off certain stimuli allow for more flexible outcomes. Human children for instance develop so slowly, which is the reason for our enormous ability to adapt to many different contexts, social or ecological.
“A crucial question is, to what degree should phenotypic variation be more developmentally contingent and plastic versus more strongly regulated by genotypic variation? The answer is not simple; indeed, what is typically found in organisms is a mixture of the two.”
The article then gets into specific, well-studied adaptations.
Deferred Adaptations
Any organism must choose between many innate survival and reproductive strategy patterns. There is incredible variability in the environments that requires human to adapt, and therefore we need to sample it before we have to act in it on our own. We cannot be so simple as to have hard and fast behavioral patterns because our environments are not that predictable. For that reason, evo devo has an important role in understanding the human. Development can be understood as the process of identifying the right strategies that would best put genetic material into the future, and where to put one’s limited resource, what tradeoffs to make.
“At the most basic level, the resources of an organism must be distributed between somatic effort and reproductive effort. Somatic effort can be further subdivided into growth, survival and body maintenance, and developmental activity. Developmental activity includes play, learning, exercise, and other activities that contribute to building and accumulating embodied capital — strength, coordination, skills, knowledge, and other qualities that will improve later survival and reproductive prospects. Reproductive effort can be subdivided into mating effort (finding and attracting mates, conceiving offspring), parenting effort (investing resources in already conceived offspring), and nepotistic effort (investing in other relatives).”
One of the biggest and broadest theories to predict adult behavior from childhood experiences is the theory of fast and slow life history strategies.
“At the broadest level of analysis, life history strategies vary on a dimension of slow versus fast. Some people adopt slower strategies characterized by later sexual development and debut, a preference toward relatively stable pair bonds, an orientation toward longer-term investments and outcomes, and allocation of resources toward enhancing the growth and long-term survival of both oneself and one’s offspring (i.e., embodied capital). In contrast, others display faster strategies characterized by the opposite pattern. Fast life history strategies are comparatively high risk, focusing on mating opportunities (including more risky and aggressive behavior), maturing and reproducing at younger ages, and producing a greater number of offspring with more variable outcomes.”
Evoking the nature-nurture debate, how do genetics play a role in these sorts of adaptations? “Differential susceptibility theory” says individuals can be biologically more sensitive to predictors of the future than others.
“Differential susceptibility research is useful in moving the field beyond debates about genetic versus environmental influences. Individuals who are high in neurobiological susceptibility to the environment appear to be most likely to detect and respond to their developmental contexts, showing conditional adaptation to environmental conditions, as per life history theory, whereas others who are low in neurobiological susceptibility appear to be more fixed in their development, or at least relatively unresponsive to normal variation in family conditions, as per behavior genetic models focusing on genetically-regulated alternative phenotypes.”
Nature provides the substrate, the potential, which has variability. Experience goes through that substrate to create behavior patterns that also have biological structure (think of all the behaviors associated with hunger or high testosterone).
Ontogenic Adaptations
“Some evolved characteristics of infants and children were specifically selected to serve an adaptive function at a specific time in development, termed ontogenetic adaptations.”
We tend to think of adults as the complete form that childhood was always building towards, but is should be known that there are adaptations for childhood and only for childhood. Why is that?
“Almost half of children in hunter–gatherer societies (the best model for human demographics before the agricultural revolution) die before reaching. Accordingly, natural selection has maintained various adaptations that serve the specific purpose of helping fetuses, infants, and children survive this intense mortality window.”
Childhood has evolved as a survival bottleneck. That should lead you to the question of why childhood is so long if it means less time before reproductive age. Deferred adaptations should explain that some, but more detail is found in this article. It should make sense that we evolved with tools for surviving childhood, particularly with regard to sociality and getting protection from adults.
