How Do We Grow Old ?

How and Why Do We Grow Old?


Can You Avoid Aging?
Why Do We Grow Old?
How Long Can You Live?

YOU may have imagined that all living things must inevitably wear out. Cars and vacuum cleaners in daily use eventually stop working. It is easy to suppose that animals age and die in a similar way. But professor of zoology Steven Austad explains: “Living organisms are very different from machines. The most fundamental defining character of living organisms, in fact, may be their ability to repair themselves.”

The way your body repairs itself after an injury is marvelous, but the routine repairs it makes are, in some respects, even more remarkable. Consider your bones, for example. “Seemingly inert when viewed from the outside, bone is a living tissue that ceaselessly destroys and rebuilds itself throughout adult life,” explains Scientific American magazine. “This remodeling essentially replaces the entire skeleton every 10 years.” Other parts of your body are renewed more often. Some cells in your skin, liver, and intestines may be replaced almost daily. Every second, your body produces about 25 million new cells as replacements. If this did not happen and all the parts of your body were not constantly repaired or replaced, you would grow old during childhood.
Children playing with a ball

Is aging caused by wear and tear?

The fact that we do not wear out was seen to be even more remarkable when biologists began studying the molecules within living cells. When your cells are regenerated, each new cell must have a copy of your DNA, the molecule that contains much of the information needed to reproduce your entire body. Imagine how many times DNA has been reproduced, not just during your lifetime in your own body but since human life began! To understand how amazing this is, consider what would happen if you used a photocopier to copy a document and then used the new copy to make the next copy. If you did this repeatedly, the quality of the copies would deteriorate and eventually become unreadable. Happily, the quality of our DNA does not deteriorate or wear out when our cells repeatedly divide. Why? Because our cells have many ways of repairing DNA copy errors. If that were not true, mankind would long ago have become a pile of dust!

Since all the parts of our body—from the major structures to the tiny molecules—are constantly replaced or repaired, wear and tear does not fully explain aging. The body’s numerous systems repair or replace themselves for decades, each in a different way and at a different pace. So, then, why do they all begin to close down about the same time?
Is Aging Programmed?

Why does a house cat live 20 years, but a similar-size opossum lives only 3 years?* Why can a bat live 20 or 30 years, but a mouse only 3? Why can a giant tortoise live 150 years, but an elephant only 70? Factors such as diet, body weight, brain size, or rate of living do not explain such diversity of life spans. The Encyclopædia Britannica states: “Locked within the code of the genetic material are instructions that specify the age beyond which a species cannot live.” Maximum life span is written in the genes. But as the end of that life span approaches, what causes all the body functions to start closing down?
Approximate Life Spans
A bee

Bee
90 days
A man

Human
80 years
A mouse

Mouse
3 years
A parrot

Parrot
100 years
A dog

Dog
15 years
A tortoise

Giant tortoise
150 years
A monkey

Monkey
30 years
A sequoia tree

Giant sequoia
3,000 years
An alligator

Alligator
50 years
A bristlecone pine

Bristlecone pine
4,700 years
An elephant

Elephant
70 years


Molecular biologist Dr. John Medina writes: “There seem to be mysterious signals that simply show up at certain times and tell cells to quit doing their normal adult functions.” He also notes: “Genes exist which can tell cells, and indeed entire organisms, to grow old and die.”

Our body might be compared to a company that has been doing business successfully for decades. Suddenly the managers stop hiring and training new staff, stop repairing and replacing machines, and stop maintaining and rebuilding the premises. Soon the business will start to deteriorate. But why did all those managers change their successful policies? That question is similar to the one facing biologists who study aging. The book The Clock of Ages says: “In aging research, one of the great mysteries is trying to understand why cells stop replicating and start dying.”
Can Aging Be Cured?

Aging has been called “the most complex of all biological problems.” After decades of effort, scientific research has not revealed the cause of aging, much less found a cure. In 2004 the magazine Scientific American published a warning issued by 51 scientists who study aging. It said: “No currently marketed intervention—none—has yet been proved to slow, stop or reverse human aging.” Although sensible diet and exercise may improve your health and lower the risk of your dying prematurely from disease, nothing has been proved to retard aging. These conclusions remind us of the words of Jesus found in the Bible: “Who of you by being anxious can add one cubit to his life span?”—Matthew 6:27.

Summing up the progress in the effort to find a cure for aging, Medina writes: “We don’t really know why we age in the first place. . . . After declaring a war on cancer decades ago, we still have not found a cure. And the process of aging is infinitely more complicated than the mechanisms underlying cancer.”
Research Leads to a Vital Conclusion

Research into how living things work and why they age has not crushed all hope of living longer. Some have found that their research has led them irresistibly to a conclusion that is vital to the understanding of aging. Molecular biochemist Michael Behe writes: “Over the past four decades modern biochemistry has uncovered the secrets of the cell. . . . The result of these cumulative efforts to investigate the cell—to investigate life at the molecular level—is a loud, clear, piercing cry of ‘design!’” Someone intelligently designed living things. Of course, Behe is not the first one to arrive at that conclusion. After contemplating the structure of the human body, an ancient psalmist wrote: “In a fear-inspiring way I am wonderfully made.”—Psalm 139:14.
A baby

‘We are wonderfully made’

If all living things are designed, then an intriguing question arises, Did God, the Great Designer, create mankind with a life span that is about the same as that of many animals, or does he want us to live longer than animals?