Why do we age? The Current Theories...
Why do we age? It is because everything wears down with time? Cars, computers, radios. Conventional wisdom tells us this is true, but humans are different because we are constantly renewing our cells. We get a cut on our finger and in 2-3 days it is back to normal. So, if our body can heal itself, and even fight disease, why can't it perpetuate our youth?
The shocking answer is that no one really knows why our bodies grow old. Numerous theories exist and we will look at the two most popular.
Theory #1. We age by design, our DNA is programmed to slowly let us degenerate.
This can be called the Gene Expression Theory Of Aging. It states that after a certain time our bodies trigger a code that slows repairs. Support for this theory can be seen in simpler organisms in nature like lobsters, coral, and sponges which show no signs of aging at all. The fact that they show no signs of deterioration suggests that some evolutionary change must have occurred as creatures became more complex. Another way to think about this theory is to look at life spans: a fruit fly lives for 30 days, a mouse 3 years, a turtle for 100 years, and a Redwood tree lives for 1000 years. What is the difference for the amount of time it takes for each to age and die? Is it a matter of their complexity, or their genetic programming?
In 1993 a landmark study by Cynthia Kenyon at the University of California San Francisco found that mutations in a single gene could double the lifespan of Caenorhabitis Elegans, a type of small worm often used in genetic studies. This one single finding provided the first step in proving the gene expression theory of aging, and sparked a wave of research for extending human lifespan.
Theory #2. Our body accumulates damage and our repair mechanisms can't keep up.
The other theory of aging states that aging is more a matter of evolutionarily neglect than intent, and that our anti-aging defense mechanisms are not yet up to snuff. Our bodies are complex and over time irreparable damage occurs in our body's tissues, cells, and DNA via random accidents in the chemistry of our body. This theory can best be termed The Stochastic Theory of Aging and has lead to the widespread popularity of everything high in antioxidants which could help keep the bodies chemistry more stable preventing the chance of accidents and damage. Aubry DeGray captures this view best in his program of SENS(Strategies for Engineered Negligible Senescence).
Possible solutions for Aging.
The realization that aging is not inevitable has lead to a paradigm shift of treating aging as a disease. The two theories battle it out in how each hopes to find a solution, or cure, to biological aging. The Gene Expression theory is hoping that genes can be identified which contribute directly to aging, and via gene therapy, be reversed or mitigated. The Stochastic theory believes that we can never outsmart our genes and we will need to create (engineer) technologies to repair the body where it is falling short.
- Ageing selected for its own sake. Joshua Mitteldorf, Evolutionary Ecology Research, 2004, 6: 1?17
- A C. elegans mutant that lives twice as long as wild type. Cynthia Kenyon, Jean Chang, Erin Gensch , Adam Rudner and Ramon Tabtiang, Nature 366(6454), 461-464 (1993)