You probably imagine that all living things end up wearing out and that there is no avoiding it. Cars and vacuum cleaners used daily end up bringing life to life. On the face of it, animals seem to age and die in a similar way. But Steven Osted, a professor of zoology, explains: "Living beings are completely different from machines. The most essential characteristic that distinguishes living beings is their ability to repair themselves."

The way your body repairs itself after an injury is amazing, but the ongoing repairs done to it are even more amazing. Take your bones as an example. "The bones look lifeless. But bone is a living tissue that constantly destroys and rebuilds itself throughout the life of an adult," explains Scientific American magazine. "In this process of rebuilding and rebuilding, the entire skeleton changes every 10 years." Other parts of your body are regenerated more frequently. There are cells in the skin, liver and intestines that change almost daily. Every second, your body produces about 25 million new cells to replace the old ones. If all this had not happened, and all parts of your body had not regularly undergone repair or replacement processes, you would have aged in your childhood years.

The fact that our bodies do not wear out seemed more impressive when biologists began to study the molecules inside living cells. As your cells change, each new cell must contain a copy of your DNA, the molecule that contains all the information needed to restore your entire body. Imagine how many times DNA has been replicated, not only inside your body, but from the beginning of the human race! To understand how amazing this is, think about what would happen if you duplicated a document on a copier and then used the new copy to make the next copy out of it. If you repeated this over and over again, the quality of the copies would decrease and in the end you would not be able to read what was written. Fortunately, the quality of our DNA does not decrease or wear out when our cells divide over and over again. Why? Because cells have many ways to correct mistakes that occur during DNA replication. Otherwise, humanity would have long ceased to exist.

Because all the parts of our bodies—from the large structures to the tiny molecules—are constantly changing or recovering, wear and tear is not enough to explain aging. The many body systems repair or replace themselves for decades, each in a different way and at a different pace. So why do they all start to go out of action at about the same time?

Is aging genetically programmed?

Why does the house cat live 20 years, but an opossum whose dimensions are similar lives only 3 years? * Why can a bat live 20 or 30 years, but a mouse only lives 3 years? Why did a giant turtle live 150 years, but an elephant only 70 years? Factors such as diet, body weight, brain size, or pace of life do not explain the differences in longevity. TheEncyclopædia Britannica states: "Within the genetic material are provisions that explicitly define the maximum age of the species." The maximum lifespan is programmed in genes. But when life is about to end, what causes all bodily functions to begin to fade?

Dr. John Medina, a molecular biologist, writes: "It seems that there are mysterious signals that simply appear at certain times and instruct cells to cease functioning as adult cells." He adds: "There are genes that tell cells and basically whole organisms to age and die."

Our bodies can be compared to a society that has been thriving for decades. Suddenly, the managers stop recruiting and training new employees, stop repairing and replacing machines, and stop maintaining and renovating the buildings. It won't be long before the business deteriorates. But why did managers change their successful policies? A similar question is raised by biologists who study the aging process. The Clock of Ages states: "One of the greatest mysteries in the study of aging is why the cells cease to renew themselves and begin to dying."

Is there a cure for old age?

Aging is referred to as "the most complex biological problem"…

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