The trick is, you want the telomeres to shorten all the way in cells that rapidly divide because this ends cell lines. And if you don't end proliferating cell l

The trick is, you want the telomeres to shorten all the way in cells that rapidly divide because this ends cell lines. And if you don't end proliferating cell lines, you get cancer. All of us and all of our tissues have cells that are basically pre-cancerous, they have driver mutations associated with cancer, and the only thing preventing them from running amok is the fact that there are limitations in the number of divisions that are possible. This is all based on information that's become visible via single-spell spatial transcriptomics. See Peter Campbell's work.