Leonard Hayflick

person · earth · Philadelphia, Pennsylvania

American microbiologist (1928–2024) who, working with Paul Moorhead at the Wistar Institute in Philadelphia, showed in 1961 that normal human diploid cell strains undergo a finite number of population doublings — of the order of forty to sixty — before arresting. The result contradicted Alexis Carrel's widely believed claim that cultured chick heart cells could divide indefinitely, and it established that ageing has a cell-intrinsic component. Hayflick also derived the WI-38 cell strain used to produce several human vaccines. He remained, for six decades, one of the most consistent public sceptics of anti-ageing claims, arguing that ageing is the accumulation of molecular disorder rather than a programme and therefore not the kind of thing a drug can be expected to reverse.