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.

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 plant's 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 wasn't 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 Mendel's 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. Darwin's ideas being assimilated into popular culture while Lamarck's work languished in obscurity. Darwin's 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 Weismann's idea of a 'barrier' [Weismann, 1885] and the central view of the genetic paradigm, which is 'reductionistic'.

Lamarck's theory alternatively, is of 'transformational' development, which results from the organism's 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 children's '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].

Epigenesist's 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