The Science of Aging

While many people search for the elusive fountain of youth, you might wonder why we age in the first place. What biological factors within our bodies or cells contribute to aging? Various internal and external factors, including diet, exercise, and environmental stress, all impact cell damage, repair, and the rate of aging. However, an intriguing fact is that, aside from these influences, we also have a biological clock embedded in our genetic code. This clock has a limited lifespan, meaning we are essentially programmed to age and die.

Our bodies consist of trillions of cells that continually divide, each time copying their DNA. This DNA is organized into structures called chromosomes, of which humans have twenty-three pairs. The challenge is that DNA replication is not perfect and tends to skip the ends of chromosomes. To safeguard crucial DNA information, chromosomes have telomeres at their ends—repetitive DNA sequences that can be sacrificed. However, with each cell division, these telomeres shorten until they are eventually depleted. When this happens, the cell ceases to divide.

Some flatworms have the ability to regenerate their telomeres indefinitely, granting them what is effectively biological immortality. Despite this, their lifespans vary and they remain susceptible to diseases, indicating that aging is influenced by both genetic and environmental factors. So why don’t our cells have this regenerative ability? In fact, this replication limit helps prevent cancer, which is characterized by uncontrolled cell growth and resistance to cell death. The point where a cell stops replicating is known as cellular senescence. In humans, this replication limit is about fifty divisions. Once reached, cells start to lose function and die, leading to age-related traits.

This also explains why life expectancy is strongly influenced by genetics, as you inherit your initial telomere length from your parents.

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