In 1961, two biologists named Leonard Hayflick and Paul Moorehead discovered that old age is built into our cells. At the time, many scientists believed that if healthy human cells were put in a flask with a steady supply of nutrients, they would multiply forever. But when Dr. Hayflick and Dr. Moorehead reared fetal human cells, that’s not what they found. Time and again, their cells would divide about 50 times and then simply stop.
Signs of Aging, Even in the Embryo
