Hayflick limit
Hayflick
Hayflick’s 1962 work established a finite replication limit for normal human fetal cells — 40–60 divisions — using culture methods and a definitive male-female co-culture experiment. It refuted Carrel’s immortality claim, distinguished mortal normal from immortal cancer cells, and produced WI-38 — the foundational cell strain for vaccine development. It did not identify the counting mechanism, nor prove cellular senescence drives whole-organism aging.