01
Genomic instability
The DNA collects typos
Every one of your cells holds the same three-billion-letter instruction book, and has to copy it perfectly, again and again, while sunlight and its own chemistry attack the pages. The proofreaders are astonishingly good. Ageing is what it looks like when the typos start arriving faster than they can be caught.
What you can dolittle you can do today
Less than anyone selling you a pill will admit. What is beyond argument is what causes the damage in the first place: tobacco, sunburn, heavy drinking. After that the useful move is not repair but detection — the scans and blood tests that find the consequence while it is still small.
The science, in one sentence
Damage builds up in the DNA faster than the repair machinery can clear it, and some of it becomes permanent.
In the glossary
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