he idea that every organism must age was a concept that surprised many biologists. For a long time, aging was thought to be a process occurring only in multicellular organisms. The reason for this arguably odd presumption was that we knew somatic cells—such as those that comprise the kidney, brain, and liver—lost their functionality over time: they aged. Furthermore, those cells divided only a limited number of times, around 50, after which they reached the so-called Hayflick limit, stopped proliferating, and died.
Unicellular organisms were thought to be capable of dividing forever, as long as conditions allowed: one generation begetting the next down through time—a sort of immortality. If unicellular organisms were like somatic cells, then they would age as they divide, reach the Hayflick limit, and die.
Shock and Age by Rick Morimoto
It wasn’t until ...
