FRIDAY, Oct. 19 (HealthDay News) -- Most of the increase in human life expectancy has occurred in the last four generations, out of the roughly 8,000 generations that have ever lived, according to a study published online Oct. 15 in the Proceedings of the National Academy of Sciences.
To investigate increases in human life expectancy in an evolutionary context, Oskar Burger, Ph.D., from the Max Planck Institute for Demographic Research in Rostock, Germany, and colleagues compared mortality patterns in modern-day hunter-gathers and low-mortality populations.
The researchers found that the mortality profile of hunter-gatherers was closer to wild chimpanzees than to low-mortality populations such as Japan and Sweden. Most of the reduction in mortality in low-mortality populations occurred over four generations since 1900. This improvement in lifespan is similar to those observed in longevity experiments in fruit flies, worms, and mice.
"The prediction that late-life mortality is determined by deleterious mutations that progressively accumulate as the force of selection declines with age is difficult to reconcile with the finding of exceptional environmentally driven malleability in mortality at all ages," Burger and colleagues conclude.