Why We Grow Old

 

Why We Get Old

The search for the fountain of youth has been going on for hundreds of years. It’s still going on today. From the tales of the wellspring of youth to anti-aging quests, we seek to slow or reverse aging. But do you know why we age? What’s it about our very bodies that make us age at a cellular level?

Methods of getting old are internal and external. How we use our energy and awareness determines how fast or slow we age. But beyond those variables there’s a bigger, biological purpose of aging. It’s in our DNA.

Our Internal Clocks

Many people deny that aging and death are part of life. Our bodies will experience them. This may seem weird but our genes have an aging clock. Aging is not just due to environmental stress or poor nutrition. It’s also encoded in our DNA.

Trillions of cells in our bodies divide over and over. Each time a cell divides it makes a copy of its DNA. This DNA is carefully organized into 23 pairs of chromosomes. But DNA replication isn’t perfect. Each time our cells divide they lose a small piece of the DNA on the ends of the chromosomes.

Enter telomeres: the caps at the end of our chromosomes. They keep the cell’s genetic information intact for its lifetime. These telomeres have repetitive DNA sequences. They don’t have important genes. They act as buffers, protecting the essential DNA during replication. But with each division telomeres get shorter and shorter.

Telomeres wear out over time. When that happens the cell can no longer divide. This is called the Hayflick limit and occurs after about 50 divisions in human cells. The cell now enters a state of senescence. It loses function and eventually dies. This is a major cause of the signs of aging.

The Problem of Immortality and Regeneration

Some species like certain flatworms can regenerate their telomeres forever. This makes them biologically immortal. They can avoid aging and dying for a long time. But even those organisms are not immune to disease and environmental pressures. This means aging is a mix of genes and environment.

Humans don’t have that potential. The answer lies in cancer prevention. Telomere shortening is a defense against cancer. Cancer is uncontrolled cell growth. Limiting how a cell can divide reduces the risk of cancer.