Before the Flood people were living hundreds of years. As man grew more evil, God declared that man’s lifespan would be reduced to 120 years. Modern biology has learned that we do indeed have built-in timers in each of our cells that limit the number of times they can divide.
Photo: Human chromosomes (grey) capped by telomeres (white). Courtesy of U.S. Department of Energy Human Genome Program. (PD)