Fifty years ago, microbiologist Leonard Hayflick demonstrated that, contrary to what was believed, human cells in a petri dish do not continue to double forever.478 They only grow and divide about fifty times before entering an irreversible state of arrested replication, known as cellular senescence.479 Senescence comes from the Latin word senex, meaning “growing old.”480 We always have immortal stem cells that can create new cells with a fresh start, but, once they form, they only have about fifty divisions before they, too, are dead in the water. This is a good thing. This natural “Hayflick
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