Overview of Programmed Theories of Aging

If the body is like a machine, then why don't we live forever? There are many theories of aging, and programmed theories of aging help explain why death is an inevitable part of being human. 

Programmed theories of aging assert that aging is an essential and innate part of the biology of humans and that aging is programmed into our body systems. Otherwise, we would live forever. The three main systems that are connected with aging are the endocrine (hormonal) system, the immune system, and our genes. These systems change over time, and these changes cause the symptoms and signs of aging.

Senior couple holding hands and walking in park
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The Body Is Not a Machine

In order to understand this concept, it is important to recognize that the body is indeed not a machine. While we like to compare the human body to a machine, this is not a very good comparison. Unlike a machine, which has only the parts it was built with, the human body continually repairs and replaces cells.

Believe it or not, every seven years, 90 percent of the cells in your body are brand new. The human body is an amazing, open and dynamic system, which is why it ages, unlike a machine.

Aging Is About Evolution

Technically, there is really no reason that the human body should "wear out," as long as it can repair and renew itself. Therefore, something other than time must be at play to cause the inevitable effects of aging.

The programmed theory of aging asserts that aging and death are necessary parts of evolution, not of biology. If a species did not have the genetic capacity for aging and death, then it would not be forced to replicate to survive.

Individuals in the species would just keep on living until a climate or other change wiped them all out. The key point here is that if biological individuals live forever, evolution would not exist.

Aging Is Programmed

Since aging is about evolution and not biology, it must be inherent in the organism and not simply a result of environmental factors or disease. That means that aging and death, according to this theory, are not a result of wear and tear or exposure, but are a programmed, natural and necessary part of genetics. In short, we are genetically programmed to age and die.

Evidence Supporting the Theory

The evidence supporting this theory is that there is not a great deal of variation in lifespan within species. Elephants die at around 70 years old, spider monkeys die at around 25 years old, and humans die around the age of 80, on average.

Some changes can be made based on nutrition, medical care, and other demographic factors, but overall lifespan within species is fairly constant. The programmed theory asserts that if aging were due to wear and tear, there would be more variation in lifespan within each species.

That said, aging and dying are inevitable, but there are things you can do to improve your chances of living a long and healthy life. Check out longevity advice for healthy aging tips.

3 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Jin K. Modern Biological Theories of Aging. Aging Dis. 2010;1(2):72-74.

  2. Spalding KL, Bhardwaj RD, Buchholz BA, Druid H, Frisén J. Retrospective birth dating of cells in humans. Cell. 2005;122(1):133–43. doi:10.1016/j.cell.2005.04.028

  3. Goldsmith TC. Externally Regulated Programmed Aging and Effects of Population Stress on Mammal Lifespan. Biochemistry (Mosc). 2017;82(12):1430-1434. doi:10.1134/S0006297917120033

Additional Reading

By Mark Stibich, PhD
Mark Stibich, PhD, FIDSA, is a behavior change expert with experience helping individuals make lasting lifestyle improvements.