The Hayflick Limit, proposed by Leonard Hayflick in 1961, is an upper bound of how many times a normal human cell (not a stem cell) can divide before it can no longer divide. For mice, the number is about 15; humans: 50; and Galapagos turtles: 110.
Telomeric Decline
“Each time a cell undergoes mitosis, the telomeres on the ends of each chromosome shorten slightly. Cell division will cease once telomeres shorten to a critical length. Hayflick interpreted his discovery to be aging at the cellular level.”
Telomeric Shortening & Accelerated Cell Death
Some researchers believe that adverse childhood experiences like physical abuse, sexual abuse, and exposure to violence, can lead to permanent accelerated cellular aging due to faster telomeric length decline.
Immortality (maybe?)
Many people believe that if we could somehow hack the Hayflick limit, we’d achieve cellular immortality – or significantly lengthen human lifespans. What if telomeres never degraded? Or could self-repair? These same people believe that breakthroughs in this area are not only possible, but inevitable; which is why lots and lots of money is pouring into this field of study.