The 4 Stages of Human Physical Development

1. THE 4 STAGES OF
HUMAN PHYSICAL
DEVELOPMENT
By: Jamie Brynn Hamilton

2. Stage 1: Infancy andToddlerhood
Summarized: Infancy and toddlerhood occurs during the first couple of years of life.The infant
begins as a newborn with very little capabilities, and ends after around 3 years, wherein the human
is now a toddler with the ability to walk, speak, and perform basic life skills.
Key Points of Growth:
■ After 1 year, the infant sees a 50% increase in their length, and after 2 years, a 75% increase
■ During the transition from infancy to toddlerhood, the human gains the ability to walk in lieu
of crawling
■ Weight doubles after 5 months, triples after 1 year, and quadruples after 2 years
■ The ability to sleep at night and remain awake for longer daytime periods increases
■ By the age of 3 toddlers are toilet trained, can walk, put on shoes, open doors, and speak

4. Stage 2.a: Early Childhood
Summarized: During early childhood the very rapid growth rates from stage 1 taper off slightly,
but the child still continues to see increases in length and bodyweight.This stage also includes
a general reduction in body fat (more so in boys than girls), as well as things such as balance,
new skill acquisition, and coordination.
Key Points of Growth:
■ An average of 2-3 inches of height and 5 pounds are gained each year
■ New skeletal developments between the ages of 2 and 6 occur
■ By the ages of 2-3 children can run, jump, hop, skip, throw, and swing, but their
movements remain slightly awkward
■ By ages 4-6 the ability to run faster and skip skillfully are acquired
■ Balance improves with time as a result of a shift to a generally leaner, more gravitationally
sound physical makeup

6. Stage 2.b: Middle Childhood
Summarized:The second stage of childhood also includes still-quite-accelerated growth
patterns, which can often be noticed in spurts.
Key Points of Growth:
■ At the ages of 6-8, girls are not as tall as boys, but the reverse is true by age 9 – which
is a solid growth period for girls
■ Girls retain high levels of body fat than boys, who retain more muscle
■ Bones are lengthening, and flexibility is at an all-time high
■ By the age of 12, all of the primary teeth are replaced by adult teeth
■ Legs tend to look very long during these years, as a result of growth

8. Stage 3: Adolescence
Summarized:This stage is largely dominated by hormonal changes that which contribute
to physical changes.
Key Points of Growth:
■ Growth spurts occur during which the body “fills out” after the lankier childhood years
■ Boys experience voice changes, generally leading to a deeper voice
■ An increase in sex hormones happens with both sexes
■ Physical developments such as breasts in girls and beards in boys appear
■ Menstruation begins for females between the ages of 11 and 14

10. Stage 4.a: EarlyAdulthood (ages 20-40)
Summarized: Humans are ”in their prime” during this stage. From a physical standpoint,
strength, sensory abilities, and overall bodily health is at its peak.
Key Points of Growth:
■ Muscle strength and cardiac function are at their peak points
■ By age 30, vision degeneration, sound sensitivity decreases (happens twice as quickly for
men)
■ By age 35, hair may become thin and gray, but genetics and lifestyle factors are an
influencer in this case
■ Towards the end of this stage, skin becomes drier and wrinkles begin to appear
■ Also towards the end of the stage, the immune system becomes less efficient and
reproductive abilities decline

12. Stage 4.b: Middle Adulthood (ages 40-
65)
Summarized: During this stage right before seniority is reached, abilities are still experiencing a
decline and all growth and peak stages have passed.
Key Points of Growth:
■ Menopause typically occurs for women around age 50: it can last from 6 months to a year
and has many possible symptoms
– Symptoms: anxiety, poor memory, inability to concentrate, depression, mood swings, decreased sex drive
■ Hearing continues to decline
■ Skin is wrinkling, age spots appear, blood vessels become more apparent
■ Fat accumulation is accelerated, as well as muscle loss
■ By age 60, the eyes lose their ability to adjust to objects at varying distances