The first large-scale studies of mortality cast doubt on the idea that there is a biologically fixed life span for fruit flies and possibly for humans. The findings suggest that after a certain advanced age, a person's chance of dying may begin to level off, according to researchers at UC Davis and colleagues, who recently published their work in the journal Science.
Previous studies -- on populations of people, most other mammals and birds -- found that death rates
gradually accelerated with age throughout the life span of an individual. But the new studies suggest that beyond a certain advanced age, death rates slow down; in other words, there is no biological clock with a preset midnight hour.
"Our research shows that the oldest individuals live progressively longer," says UC Davis entomology professor James Carey. Carey and his co-authors followed the lives and deaths of more than 1 million Mediterranean fruit flies to find out if the death rates at advanced ages would imply an upper life-span limit. They did not.
"The notion that there's some fixed limit to a person's life, which you inherit from your parents, is overly simple," says co-author James Vaupel, a population analyst at Duke University's Center for Demographic Studies.