We all grow old, and we all die. Let’s explore the possible forces that are at work in this process. Is it predetermined how fast we will age and when we will die, or is it dependent on the amount of damage our cells are exposed to?

Aging and Death

Both aging and death are biological events. Everyone ages over time, and eventually, everyone dies; it is the cycle of life. We all know this. But do we know why?

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Researchers have not identified a specific, single cause, but they have some good ideas about what is going on. Let’s meet two researchers who are investigating the mystery behind aging and death. First, we have Wanda, who is researching damage theories. Next, we have Frank, who is researching programmed theories. Both of the theories being investigated are important keys to understanding why we grow old and eventually die.

Damage Theories

We will let Wanda explain damage theories to us first. Damage theory is the idea that external or environmental forces gradually damage cells and organs, leading to aging and death. There are many specific sub-theories of this theory.

Examples include:

  • Living theory
  • Free radicals theory
  • Cross-linking theory
  • Wear and tear theory
  • Theory of error catastrophe
  • Somatic mutation theory

Each of these individual damage theories focus on a different external or environmental factor, but they all examine how slow and continuous damage to cells will eventually lead to cellular dysfunction. Damage theories do not rely on a pre-determined timeline for aging and infer that we could increase our lifespan if we take steps to protect our bodies from cellular damage.

Let’s look at one specific example more closely. Imagine that Wanda is investigating free radicals theory. She is trying to find out how oxygen free radicals affect cells. These free radicals are a product of normal cell metabolism, but the amount of free radicals a cell has to deal with can be influenced by environmental factors.

Wanda discovers how this waste product can build up and damage cells over time through oxidation. This damage will eventually cause the cell to stop functioning. This is similar to oxidation causing rust on a metal hinge. The rusty hinge will eventually stop working.

Programmed Theories

Now let’s let Frank explain programmed theories. Programmed theory is the idea that aging is genetically programmed to occur with time, and this process of deterioration eventually leads to death.

Programmed theory also has specific sub-theories, such as:

  • Endocrine theory
  • Programmed senescence theory
  • Immunological theory

Each of these programmed theories focus on a different genetically programmed trait that is responsible for aging, but they all rely on the concept of an internal biological clock to explain the process. Proponents of programmed theories believe that since early growth and development is genetically programmed to follow a predetermined timeline, it’s logical to assume that the changes that occur with aging might follow a genetically programmed timeline as well.

Let’s look at endocrine theory as an example. Imagine Frank is investigating endocrine theory. He is trying to determine how our hormone levels control the pace of aging. Frank notices that the production of certain hormones declines with age. This leads to changes in our bodies that are responsible for some of the effects of aging.

Interaction of Theories

So, which theory of aging is better, damage theory or programmed theory? There is no right or wrong answer to this question because, in reality, both theories and their sub-theories are interlinked.

For example, even if the decision for when cells will die is genetically programmed, the exact timing might vary depending on the amount of damage to the cell. This means that some age-related changes may be programmed, while other age-related changes are based on cell damage.

The aging process is quite complex, so the probability that any one theory could satisfactorily explain it is extremely unlikely. It is clear that both genetics and wear and tear over time both play a role. The study of the aging process is also complicated by the need to distinguish the aging process itself from the effects of disease.

Lesson Summary

Two possible theories that could explain aging and death are programmed theory and damage theory. These theories are not exclusive and work in interaction with one another.

Programmed theory is the idea that aging is genetically programmed to occur with time, and this process of deterioration eventually leads to death. Damage theory is the idea that external or environmental forces gradually damage cells and organs, leading to aging and death. Each of these theories consists of different sub-theories that are being investigated by researchers. The aging process is quite complex and cannot be explained by one theory alone.