THE 4 STAGES OF HUMAN PHYSICAL

DEVELOPMENTBy: Jamie Brynn Hamilton

Stage 1: Infancy and ToddlerhoodSummarized: 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

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

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

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

Stage 4.a: Early Adulthood (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

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