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Leonard Hayflick

Leonard Hayflick is a Professor of Anatomy at the UCSF School of Medicine, and was Professor of Medical Microbiology at Stanford University School of Medicine. He is a past president of the Gerontological Society of America and was a founding member of the council of the National Institute on Aging (NIA). The recipient of a number of research prizes and awards, including the 1991 Sandoz Prize for Gerontological Research, he has studied the aging process for more than fifty years. He is known for discovering that normal human cells divide for a limited number of times in vitro (refuting the contention by Alexis Carrel that normal body cells are immortal). This is known as the Hayflick limit. His discoveries overturned a 60-year old dogma that all cultured cells are immortal. Hayflick demonstrated that normal cells have a memory and can remember at what doubling level they have reached. He demonstrated that his normal human cell strains were free from contaminating viruses. His cell strain WI-38 soon replaced primary monkey kidney cells and became the substrate for the production of most of the world's human virus vaccines. Hayflick discovered that the etiological agent of primary atypical pneumonia (also called "walking pneumonia") was not a virus as previously believed. He was the first to cultivate the causative organism called a mycoplasma, the smallest free-living organism, which Hayflick isolated on a unique culture medium that bears his name. He named the organism Mycoplasma pneumoniae.

In 1959, Hayflick developed the first inverted microscope for use in cell culture research. To this day, all inverted microscopes used in cell culture laboratories worldwide are descended from this prototype. His microscope was accessioned by the Smithsonian Institution in 2009.

Hayflick developed the first practical method for producing powdered cell culture media in 1965. This method is now used worldwide for the production of many tons of powdered media annually for use in research laboratories and commercial production facilities. The technique is not patented and Hayflick receives no remuneration from this invention.

Hayflick is the author of the book, How and Why We Age, published in August 1994 by Ballantine Books, NYC and available since 1996 as a paperback. This book has been translated into nine languages and is published in Brazil, the Czech Republic, Germany, Hungary, Israel, Japan, Poland, Russia, and Spain. It was a selection of the Book of the Month Club and has sold over 50,000 copies worldwide.


  • –present
    Professor of Anatomy, University of California, San Francisco