Human Life Cycle


Human beings are culture-bearing species that fall under the genus Homo and the family Hominidae. In appearance, human beings are physically similar to apes. Earlier, only human beings were the species exclusive to the family Hominidae. But a recent study suggests that chimpanzees are more closely related to humans than gorillas and the last mutual ancestor amongst humans and chimpanzees, lived about 6 to 7 million years ago.

A human body consists of hour limbs; which is the two arms and legs, a head and neck attached to the torso. The shape of the human body is formed from a strong skeleton which is made of bone and cartilage, covered with fat, muscle, organs, tissue and so on.

The difference between apes and human beings is that humans have a far more developed brain. The body structure of human beings is erect and showcases movable hands. Between human beings and ancient apes, cognitive ability has become similar as these apes show great cognitive abilities, which was believed to be unknown to human beings.

The human body undergoes numerous changes and developments since conception. The food humans eat, helps them to develop. If we look at this historical trail of human evolution, there are many highlights to be looked upon. But for now, let’s look at the life cycle of a human being to get a better understanding.

Life Cycle of Human

The following is the different stages of development in the human life cycle

1) Pregnancy:

The sperm from the adult male human and the egg from the adult female human form a zygote inside the uterus of the female. Over time, the zygote develops and forms into an embryo. Initially, the embryo looks like a cluster of cells, but after eight weeks, the embryo resembles the human body and is called a foetus. The developing embryo is called foetus during this stage. During this stage, the foetus is entirely dependent on the female for breathing, eating and other kinds of resources.

2) Infancy:

After around nine months, the foetus is fully developed to be born. This stage in human development marks the period from birth to age one. Infancy is the earliest part of childhood, where the infant grows in size and shape. During this stage, the infant requires a lot of attention as they are completely dependent on their mothers. Infants develop their behaviour, physiology and cognition. Gradually, the infants learn to suck, swallow and cry if they are in an uncomfortable situation. Since the infants are unable to speak, crying is their way of communicating. The mother tends to breastfeed their infants during this stage.

3) Toddler years:

The term ‘to toddle’ means to walk unsteadily and the child has a clumsy walk during this period. This stage marks the end of early childhood. During this period, the child ages two to three years old. This stage in a child’s life is where they undergo immense cognitive, emotional and social development.

4) Childhood:

Here, the child ages from three to six years of age and is crawling for mobility. In this stage, the child crawls and eventually learns to walk, talk, eat independently, and become more aware of their surroundings. The child is more social and active during this period and intrigued to learn new things.

5) Adolescence:

Here, the child ages from nine to thirteen years of age and this period mark the beginning of adolescence. In this stage, the child grows into an adolescent, through a period called puberty. Puberty occurs during the initial stages of their teenage years, and that’s why adolescents are also called teenagers. In this stage, the teenager grows rapidly and physical changes begin to appear. These changes include hair growth, structural changes in body shape, voice cracking in adolescent males, breast growth in adolescent females and so on.

The behaviour pattern also changes, as they are more independent in performing daily tasks.

6) Adulthood:

Human beings who age from 20 to 60 years of age are known as adults. Here, human beings are sexually mature and capable of reproducing. The body is fully developed by now, and the adult gains experience and responsibility. Adults have full mental and social development by this stage.

7) Middle age:

The time period of adulthood that starts from 30 to 50 years of age.

8) Old age:

When a human being reaches 60 or 65 years of age, they are called old people. This period starts from 65 years of age, until the end of their lives. During this stage, the intestine absorbs fewer nutrients from food sources. The physical capabilities of doing tasks also reduce and they again depend on external support to do things.

The behaviour of old people in this stage varies, depending on the immunity and lifestyle of the human. The average life expectancy of human beings varies from 70 to 85 years. But this also changes depending on their lifestyle.


A human being’s body undergoes several changes and developments throughout their life span and food acts like the fuel needed for all these changes. Proper nutrition, exercise and friendly environment ensures a healthy human being in all stages of their life. Some basic nutrients required for human growth are carbohydrates, essential amino acids, fatty acids, vitamins and minerals in order to sustain a healthy lifestyle.

Frequently Asked Questions on Life Cycle of Human

What are the six stages of the human life cycle?

The six stages of human development include pregnancy, infancy, toddler years, childhood, puberty, adolescence, adulthood, middle age and senior years.

What are the characteristics of human development?

The growth of different characteristics that occur is body structure, aptitude, intelligence, height, weight, hair colour, and sexual orientation.

What are the main objectives of human development?

The main objectives of human development include health, education, physical development and freedom. The objectives should also include human rights, social, economical and political freedom.

To explore more information on human beings and other species, register with BYJU’S Biology.

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