The developmental life course
 
Aim:  To provide examples of how biological features of human growth & development are influenced by a variety of social factors.
 
Human Development 每 lifelong process of personal development: birth ↙ death
 
Across the life course, biology is the overall developmental organiser but social factors also play a very important part eg research shows that babies born to poorer families are more likely to be born premature, are at greater risk of dying during infancy & are more likely to experience poverty, impaired development and chronic disease in later life.
 
Prenatal life
 
All human beings begin life as a single cell, formed when male sperm & female egg fuse at conception 每 1^st part of the life course (prenatal phase).  That single cell carries in its nucleus the genetic code for the adult it will become.
 
After conception, the single cell embryo splits into 2 ↙ 4 ↙ 8 ↙ 16 etc.  This cell cluster travels along the fallopian tube to the womb where it implants.  By 38 wks qround 25 trillion (25 million million) living cells will emerge as a human baby from its mother＊s womb.  The neonate (newborn baby) will then grow, through childhood & adolescence, into an adult human being with approx. 100 trillion cells.
 
The uterine environment that the mother provides has a major impact on foetal development and on postnatal life.
 
Research suggests that some of the effects of our life in the womb might not be felt until decades after our birth 每 in particular, the uterine effects on foetal health are linked to the lifestyle choices of the mother.
 
Infancy
 
As babies, we are born with biologically based dispositions & potentials that affect our growth & development.  These dispositions & potentials require appropriate social support & ＆triggers＊ for them to unfold.
 
Genes contain biological instructions for a person＊s growth & development which are shaped by the social environments 每 home, school, work 每 that the person experiences.
 
Newborn infant 每 weighs around 7 lb ( 3.4 kg), length 每 20 ins (51 cm).  Boys 每 larger & heavier than girls.  After 6 mths, infants from affluent homes grow faster than infants from poorer backgrounds.  This is due to better nutrition, fewer illnesses and higher standards of health in affluent families.
 
Affluence & poverty also affect the infant mortality rate (number of deaths of children under one year old per 1000 live births). See chart p174.
 
Socioeconomic status (where they live) of an infant＊s parents also affects life expectancy:
 
1997 - 9           male life expectancy   71.1 yrs           unskilled groups
1997 每 9          male life expectancy   78.5 yrs           professional groups
 
(gap of 5.7 yrs for females)
 
Early & middle childhood
 
Growth rates for boys & girls 每 similar until age 10.  Girls then experience a growth spurt that peaks at age 12, boys enter a period of rapid growth 2 -3 yrs later.
 
As humans grow, infancy ↙ early childhood, their brains grow too.
 
Age 6 每 brain is 90 每 95% its adult size.
 
Age 6 每 12 brain cells grow bushier, each cell making lots of new connections to other brain cells & setting up new pathways for nerve signals.
 
 Process peaks when girls aged 11, boys aged 12.
 
These are only general patterns 每 children＊s health profiles can move in the direction of advantage or disadvantage according to genetic, social & other circumstances eg children from poorer social backgrounds are more prone to disease than children from more advantaged backgrounds.
 
Health & social professionals are confronted daily with the damaging & steadily increasing effects on child development of poverty, poor housing & dangerous neighbourhoods.
 
Adolescence
 
In a biological sense, adolescence begins with the onset of puberty & ends with brain maturation around age 25.  In social terms, adolescence ends at a time when an individual assumes adult responsibility.
 
Adolescence is characterised by rapid physical growth & the onset of maturation.
 
Girls usually experience the start of menstruation between age 11 每 13.  Boys are able to ejaculate live sperm around 14 yrs of age.
 
Girls younger than 15 still have immature reproductive systems, putting their infants at risk of prematurity & low birth rate.
 
In developmental terms, adolescence is a life stage in which people experience a ※vastly growing intensity of impulses§.  Biological brain research has shown that the adolescent brain undergoes a lot of change & development.  This affects both the mental & emotional functioning of teenagers.  The sex hormones are especially active in the adolescent limbic system  (the emotional centre of the brain).  As a result, adolescents＊ feelings can be on a very short fuse.  Unfortunately, the part of the brain that puts the brake on risky impulsive behaviour 每 the prefrontal cortex 每 is the last area of the brain to mature.  This means that the brain structures that seek strong sensations & excitement are on full throttle while the more ＆sober＊ parts are still under construction.  This is illustrated by young male drivers who overestimate their driving skills, with sometimes devastating results for both themselves & their unintended victims.
 

Adulthood
 
Females 16+ and males 18+ grow very little, but growth varies from person to person.  Peak health, as measured by heart & lung function, is reached by 20's or early 30's.  Variations in the health status of young adults is usually socially induced, some of which can be traced back to childhood circumstances.
 
Middle age has been characterised as the period during which an individual's "broad mind & narrow waist" trade places and a few more inches of fat in midlife are not uncommon.
 
Western women experience the menopause (the cessation of periods) at around age 51.  Although the male menopause is mentioned, male reproductive function does not undergo any dramatic change - healthy men can produce sperm & have sex as long as they live!  A healthy midlife for both males & females is influenced to some extent by past circumstances & habits.
 
Late adulthood begins around age 65, when many people retire.  The physical deterioration associated with late adulthood, which includes reduced muscle mass & weaker bones is already underway from age 60+.  However, many older people enjoy a very active old age & retirement by taking part in activity that is physically, socially & intellectually stimulating & challenging - social factors continue to interact with physical processes of ageing to promote new forms of personal 'development'.