Development is a process that starts from conception to death (from womb to tomb). It is a continuous and an on-going process that evolves in a stage by stage manner. Our interest in human growth and development infers from our concern about human behaviour and its manifestations. As Biehler (1976) has argued, “since experiences during childhood and adolescence apparently have a significant influence on later behaviour shouldn’t it be possible to observe how children develop and how they are influenced by experience, in order to find ways to help people live happy fulfilling lives?” (p.17). This concern for human behaviour and human development can be traced to the time of Plato and Aristotle, and it is interesting to note that some of the observations of Plato and Aristotle on human development are still very current and useful to modern developmental psychologists and child rearers. Our knowledge of developmental psychology would help us understand the processes through which children pass side by side with the various experiences they encounter as they grow and develop. These will help us mould human behaviour from initial developmental stage to the terminal stage of human development. Such systematic moulding of human behaviours will help to make our society better and the societal environment a better place for us to live.
Human life and development begin in the mother’s womb as a result of the donation of 23 chromosomes from the father and 23 chromosomes from the mother, making total of 46 chromosomes out of which each individual is conceived. Human life begins here and from now on, he or she begins to grow and develop. By this chromosomes blend, the conceived individual has received the genetic characteristics of his or her parents even up to the distant generation both paternally and maternally. Thus, the blue prints for what the individual will be intellectually: behaviourally and trait – wise, have been laid by this blend of chromosomes. At the time this individual’s conception live begins, the individual happens to comprise only one cell which according to Biehler (1976), “ is about the size of a pinpoint” (p. 151). Eventually this one cell will transform into sixty trillion cells; each looking – alike structurally but differing in functional performance.