Describe the Processes by Which Genes and Environment Operate Together to Influence Development. Discuss the Significance of These Processes for Our Understanding of Child Development.
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CHILD DEVELOPMENT ED209
BOOK 1 : The Foundations of Child Development
T M A 02
Essay
Option 2
Describe the processes by which genes and environment operate together to influence development. Discuss the significance of these processes for our understanding of child development.
This essay will look firstly at the ideas that have prevailed throughout history, in relation to genes interacting with the environment, and the human developmental implications of this relationship. It will briefly outline the theory of Heritability, Evolution, Genetic Determination, Epigenesis, Developmental Plasticity and a transactional model of development. Secondly the theories of Genetic determination, Epigenesis and Developmental Plasticity will be compared. Physical and psychological characteristics of child development will illuminate the differing viewpoints held by these traditions. Anatomical development, temperament and language will be used as illustrators.
Since the sixteen hundreds scholars interested in the origins of human formation; believed that humans had not changed since the creation of Adam. In essence what was needed to create a human was there at the point of conception, it just got bigger [Hartsoeker, 1694 cited in Richardson, 1994 p51]. That all humans go through an unfolding process during development, which is all part of a natural plan this was referred to as Preformationism. These innate processes or stages were referred to as maturation and this has developed from the philosophical position of Rationalism. This position remained until the eighteen hundreds when biological developments challenged this position.
Gregory Mendal, [1865] showed that a plants single characteristic such as colour could be inherited or altered though cross-hybridisation. That plants possessed individual traits genes that could be altered and passed on to descendents. It wasnt until DeVrise, Corrnens and Tschermak work in the twentieth centaury [cited in Sturtevant, 1965 and Weinsten, 1977] showed that single gene inheritance etc was responsible for evolutionary characteristics in humans, an example of single gene effects can be shown in the case of PKU [Phenylketonuria] which left untreated (not stopping Children with the mutated gene eating phenylalanine in their diet) would cause retarded intellectual development. [Plomin, DeFries, and McClern, 1990, cited in Richards, 1994 p214]. It appears that Mendels accomplishments on the laws of inheritance were surpassed by the attention that was being given to the questions concerning the mechanism of evolution. [Bateson, 1909, Dunn, 1965].
By 1859 the Genetic and Epigenetic Paradigms had been proposed. Darwins ideas being assimilated into popular culture while Lamarcks work languished in obscurity. Darwins theory of Evolution proposed natural selection and adaptation, that an organism could only change as a result of mutation, a change in the genotype and that mutation had to infer an advantage in the environment (phenotype) to be selected and therefore passed on. This process according to Darwin occurred below the level of consciousness [Darwin, 1859]. The organism is in essence blocked off from its experience, leading to Weismanns idea of a barrier [Weismann, 1885] and the central view of the genetic paradigm, which is reductionistic.
Lamarcks theory alternatively, is of transformational development, which results from the organisms experience of its environment [Lamarck, 1809]. Its prerequisite is that of the organism being open to the experiences of its environment. Interaction occurs at the genetic and environmental levels. Hence logically leading to the Epigenetic paradigm, which supports the same holistic, arrangements proposed by Lamarck [Burkhardt, 1977].
Two traditions with developmental implications were influenced as a result of the differing viewpoints of Darwin and Lamarck; they were Genetic Determination and Epigenesis. Genetic Determination sees human development as reaching an endpoint; this is in essence preformational. The environment is only there to explore where childrens natural abilities lie. Development is pretty much biologically pre-ordained both in process and in endpoint. Enzymes make hand genes, which turn into hands [Torrez, 1971 p243 cited in Richardson, 1994 p62]. Developmental characteristics have no environmental input. The environment act as the canvas on which the painting will be painted, but the idea is already in the artists mind. This is drawn from a Rationalist tradition. Genetic Determination also subscribes to the idea that only genes that infer an adaptive advantage are passed on; Richard Dakwins emphasized this point when he coined the term selfish gene [Dakwins, 1976]. Therefore environmental change adaptation under these circumstances would be very difficult [Plotkin and Odling-Smee, 1979 cited in Richardson p 64]. The implications on development are, it has a pre-ordained endpoint. Which is ok for physical characteristics such as feel, teeth respiratory organs etc., which are present in all members of the species; that the genes that code these characteristics are canalised even in extreme environments [Mayr, 1970 cited Richardson, 1994 p66]. There are therefore limitations on every characteristic that once an endpoint is reached no more development can occur. Psychological characteristics however continue to develop. Genetic Determination would find it harder to explain personality, temperament, intelligence, knowledge and social adjustments, concepts which all imply that the environment is not static but fluid as are these characteristics [Richardson, 1994 p64].
Epigenesists on the other hand believe that during development a characteristic can be modified by feedback from the environment, those genes have self organising properties, which can be switched on and off in response to environmental changes. This process allows a myriad of possibilities to occur in the same developmental characteristics [Ford, 1975, Mayr, 1970 cited in Richardson, 1994 p66]. Piaget, [1980] referred to this as epigenetic