Hayflick limit
The idea of the Hayflick limit was suggested by American anatomist Leonard Hayflick in 1961, at the Wistar Institute in Philadelphia, Pennsylvania. Hayflick showed that a population of normal human fetal cells in a cell culture will divide between 40 to 60 times. The population then goes into senescence. This refutes the idea of Nobel laureate Alexis Carrel that normal cells are potentially immortal.