What Are the Different Theories of Aging?


Aging is a natural process of human development. Your body experiences many changes throughout life. Over time as you transition into geriatric life stages, your biological functions change as well—several functions, such as fertility, memory function, and immune system health, decrease as you age. The number of cells surrounding many organ systems also decreases. There are many conflicting theories on what causes aging, but what are the three major theories of aging?

What Is the Evolutionary Theory of Aging?

The Evolutionary Theory of Aging explains why organisms transition into different stages of life and into mortality. The definition of aging is also known as maturing of the body where a decline in functioning occurs with time. Many theorists and biologists have spent their lives studying various organisms and their evolution into elderhood. Reproduction is the main focus of most organisms, including humans. A great deal of the evolutionary theory of aging was formed around Darwin’s theory of natural selection. You may recall his theory focused greatly on inherited traits that keep a species alive and reproducing. 

The Evolutionary theory focuses greatly on the idea that organisms reproduce more than necessary to anticipate that not every offspring will survive. If one offspring survives, they inherently pass this survival instinct down to their offspring, who pass it to theirs—attempting to answer life’s puzzling questions, though fascinating to learn about, often requires ongoing research. 

What Are the 4 Theories of Aging?

Many theories of aging attempt to explain why organisms age. Some of them contradict one another as science has not agreed on one theory over another. To understand this topic better, you might want to consider these four theories of aging: 

  • Oxidative Damage Theory - This theory is also known as the Free Radical Theory of Ageing. Oxidative stress in the body causes damage to cells which affects how other organ systems operate. If the body cannot neutralize this damage over time, the free radicals cause cell death and organ failure. Free radicals are negatively-charged molecules that contain an extra electron. They attach to healthy molecules and pollute them with their negatively charged chemicals. 
  • Damage Accumulation Theory - This theory suggests that their ability to repair damaged DNA declines as people age. It’s like an assembly line in a factory run by machines where one machine goes down, and the line continues to run. Everything produced on that line comes through incomplete or damaged. This damage builds up in the cells over time, causing them to stop functioning or cross signals and damage other cells. 
  • Epigenetic Theory - This is also known as The Information Theory. This concept theorizes that your environment greatly affects how your genes and DNA express themselves. Kidney cells will express themselves as the kidney, and your liver cells will become part of the liver. This is called the epigenome. The epigenome determines what parts of the DNA should turn on and turn off to express or suppress specific genes. Over time your environment can cause damage to this mechanism. Kidney cells may start to express themselves as liver cells, and the body goes haywire eventually.  
  • Group Selection Theory - You may also hear this theory called the Kin Selection Theory. This concept suggests that death and aging are a part of maintaining the group’s well-being and longevity. The death of the elderly creates more resources and opportunities for the young, which ensures the species’ survival. 

What Are the 3 Types of Aging?

You will find there are three different types of aging; psychological, biological, and social aging. Psychological aging relates to behaviors as well as cognitive changes. Biological age determines the rate at which you age. Biomarkers measure your biological age, and are highly dependent on your diet, lifestyle, level of exercise, and chromosomal changes over time. 

You will find this differs from chronological age as that is numerical and begins from the time you are born. You may even feel older or younger than you are. Social age encompasses a person's interactions with their community. Staying connected with social groups and part of a family or community increases your life and strengthens your immune system. 

What Are the 4 Stages of Aging?

Can aging be described in stages? What age is considered geriatric, or middle aged? You might have heard of Gene Cohen; he was an American psychologist who expanded upon Eric Erickson’s research on geriatric aging. He wrote a book on the 4 stages of Aging called The Mature Mind. His book describes aging in a much more positive way and that the mature mind is always able to grow and develop new memories. He describes the categories of aging as follows:

  1. Phase I - You might know this as midlife. Midlife Revaluation occurs during your late 30s to mid-60s. During this phase, you may search for the meanings in life. You may begin to consider your mortality and think about getting more out of life. 
  2. Phase II - This phase occurs during the retirement years, usually between the late 50s and into the 70s. People are often more open to adventure because they feel like now is as good of a time as any. 
  3. Phase III - This phase is known as the “Summing Up,” which occurs from the late 60s through the 80s. During this stage, you are more interested in the legacy you will leave. You may want to pour into your grandchildren/great-grandchildren or volunteer somewhere. Some people write an autobiography or enjoy scrapbooking family memories. 
  4. Phase IV - This is known as the Final Phase or Encore. This stage of life happens from the late 70s up until the end of life. Keeping up with healthy lifestyle activities and exercise will allow the brain to have the best chance at staying sharp. At this stage of life geriatric care is vital to maintain a healthy life. Full of wisdom, many during this stage of life adapt well to changes and have an attitude of celebration and appreciation for life.

What Is Psychological Aging?

Your psychological age refers to how old you feel and act. This is one of the three theories of aging. Your level of maturity may differ from your chronological age. Psychological age is determined by cognitive, motor, and sensory functions.  As you age, it is believed that people experience a decline in psychological age, but this is not always the case. With proper psychologically engaging support, you can continue to grow in maturity and psychological awareness. Just as exercise maintains the physical attributes of the body, continuing the process of learning new things and engaging your senses may help support psychological aging. 

What Is the Process of Aging?

You may have heard the term geriatric, which comes from the scientific study of aging, known as Gerontology. The aging process is the natural decline in cognitive, biological, and physical health throughout the body over time.  

The factors of aging are greatly determined by how you take care of your body. Certain body functions may decline and slow down, like digestive functioning, memory retention, and physical abilities. 

What Is Sociological Aging?

There are many sociological aspects to aging that you may not consider until experiencing certain situations. As you age, social changes occur, like your support circle may decrease as some of your friends and relatives pass away. Often elderly people report a reduction in financial wealth as they leave the workforce and rely on social security and retirement. 

There are also societal stereotypes that come with age. You often are not taken as seriously and thought not to have the cognitive abilities you once had. It can become a very frustrating time for some aging people. Some people feel a sense of worthlessness that may lead to depression. This is not always the case. Some cultures are very embracing of this societal role and hold the elderly in high regard. 

What Are the Biological Theories of Aging?

The answer to what are the biological theories of aging is divided in two separate categories; the programmed and error/damage theories.  These two theories suggest that biological aging results from either a natural yet inevitable downward progression of bodily functions or resulting DNA damage from harmful environmental factors. 

The programmed theory contains multiple subcategories:

  • Programmed Longevity - Aging occurs because of specific genes that turn off and on
  • Endocrine Theory - Hormones control the process of aging.
  • Immunological Theory - The breakdown of the immune system leads to infection, disease, and death. 

The Error/Damage Theory also has several subcategories:

  • Wear and Tear - The wear and tear theory is when systems within the body begin to break down over time, causing parts of the body not to function as they should. These system failures progress and affect other areas leading to death. 
  • Rate of Living Theory - This theory suggests that every living organism has an exact number of heartbeats, breaths, and days predetermined before being born.  
  • Cross-linking Theory of Aging - This theory describes the cross-linked chemical changes between glucose attaching to protein cells. This process, over time, results in bodily damage. 
  • Free Radicals Theory - As mentioned earlier, this theory presents the idea of free radicals, which are negatively-charged molecules containing extra electrons that attach to healthy molecules and pollute them. This process, over time, causes aging and destruction within the body. This process is heavily influenced by the environment and lifestyle choices.  

You Should Consider Supplements

There are many theories on why you age the way you do. This natural and inevitable process continues to puzzle scientists. There are many ways to support this process and help you maintain health as long as possible. SpermidineLIFE creates supplements that help support processes that promote longevity such as immune health, memory function, and detoxification. SpermidineLIFE contains spermidine, a naturally occurring polyamine conducive to longevity that is beneficial for geriatric patients. Spermidine boosts the immune system and creates defenses against degenerative diseases and the harmful effects of aging. 


  • Don Moxley - Director of Applied Science

    Don Moxley is the Director of Applied Science at Longevity Labs. Moxley draws upon his career as an athlete, a sports scientist, and an instructor to lead and educate on the science of autophagy and longevity.