The pre-adult stages of growth for humans are infancy, childhood, juvenile and adolescence. Let us register the key features of each stage:
Infancy – complete dependence stage
Infancy (derived from the Latin word infans, means “unable to speak”) is period of growth of human offsprings when they are completely dependent on their caregivers (e.g. parents, elder siblings, grandparents); a stage of growth where they cannot exactly communicate their needs and the caregivers have the responsibility of proactively taking care of the infant. Interestingly, the duration of infancy is culturally determined and it varies anywhere between one to two years of age. Around two years may be a good estimate of the median age of infancy across cultures.
Childhood – semi-independent stage
It’s the post-infancy phase of growth of human babies wherein they attain increasing independence – emotionally and physically – from the caregivers and it ends with significant independence from the support of caregivers in daily routine activities; for instance, by the end of childhood phase expect them to be eating, bathing, dressing independently and to start firming up a ‘mind of her own’.
It’s mostly agreed that childhood continues broadly up to the age of 7 years. You may be wondering that over 5 years (between the end of infancy at nearly 2 years to the end of childhood at nearly 7 years) may be too long a time for gaining physical independence in daily activities.
You’re very right! The childhood years are essentially focused on the fuller development of the brain and the physical growth – the growth of the body – is a secondary target of growth. In fact, preparing for physical growth is the target of the next phase of growth of human offsprings. The human brain achieves full development, physically, by the end of this stage.
Understanding the nature of childhood helps to explain why humans have lengthy development and low fertility, but greater reproductive success than any other species.
Juvenility – stage to prepare the body for growth
It’s the post-childhood stage, beginning around the age of 8 years and continues till the time we hit puberty – a phase of nearly 4-5 years.
It may be added that this Juvenile stage must not be confused with the legal definition of the Juvenile age of ‘up to 18 years’. The legal definition need not be biologically and developmentally proper and it actually merges all the four stages of growth – infancy, childhood, juvenile and adolescence – into a broad category of ‘children upto the age of 18 years’ and titles it as juvenile.
This stage typically represents increasing freedom of thinking and action, developing further on the near independence achieved by the end of childhood. Incidentally, it begins around the age of 7 when the first permanent molars come out, and brain has (weight-wise) completed its growth.
Adolescence – stage to grow the body to adulthood
At this stage of development, children attain maturity
in all aspects necessary for physical survival (socially, economically and legally they continue to be dependent/minor).
Human adolescence begins with puberty. The adolescent stage includes development of the secondary sexual characteristics and the onset of interests and activities of adults – a far complex cognitive behaviour compared to juveniles.
These physical and behavioural changes of puberty occur in many species of mammals. However, what makes human adolescence different is that during this life stage, both boys and girls experience a rapid acceleration in the growth of virtually all skeletal tissues – the adolescent growth spurt (in the physical sense).
The two important imports for parents from the distinct stages of growth are –
1. Childhood years lay the critical ‘personal and emotional foundation’ for life
2. Juvenile years sow the seeds of ‘social development’ that continues to evolve/mature in the years following adolescence.
