Why we age – Listen to Leonard Hayflick talk about his discovery

The Hayflick Limit is a concept that helped to explain the mechanisms behind cellular aging and was fundamental in the discovery of Telomers.

The concept states that a normal human cell can only replicate and divide forty to sixty times before it cannot divide anymore, and will break down by programmed cell death or apoptosis. The concept of the Hayflick Limit revised Alexis Carrel’s earlier theory, which stated that cells can replicate themselves infinitely. Leonard Hayflick developed the concept while at the Wistar Institute in Philadelphia, Pennsylvania, in 1965. In his 1974 book Intrinsic Mutagenesis, Frank Macfarlane Burnet named the concept after Hayflick.

Listen to the man himself talk about this concept.


And activities then centred on the chromosomal characterisation of the cells, because it was by this time learned that as the cells approached their… their limited capacity to replicate, a state that I call ‘Phase three’ – I described the lineage of these cell populations as phase one, which is the period of the primary culture, phase two is the 40 or so period where the cells are actively dividing, and phase three is a period when the cells have stopped dividing.

People generally have called phase three the ‘Hayflick Limit’; perhaps I should say a word about the derivation of that term. The derivation occurred in the mid-’60s by a gentleman well-known in the scientific field, at least that time, Sir Macfarlane Burnet, an Australian Nobel Prize laureate who knew about my work and, indeed, made a visit to the Wistar Institute to see Hilary at one time and I was introduced to him then. He went on to write books in several fields outside of the one that he was expert in, which, namely, immunology, and he did a book in which he discussed aging. And in that book, he called what I had observed the ‘Hayflick Limit’, which is the origin of that term. So, I have Sir Macfarlane Burnet to either thank or not for the use of that term.