The existence of methods for correcting DNA copy errors

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.

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