Using fruit flies, NIH researchers provide molecular basis for theory of aging.  A shorter life may be the price an organism pays for coping with the natural assaults of daily living, according to researchers at the National Institutes of Health and their colleagues in Japan. The scientists used fruit flies to examine the relationship between lifespan and signaling proteins that defend the body against environmental stressors, such as bacterial infections and cold temperatures. Since flies and mammals share some of the same molecular pathways, the work may demonstrate how the environment affects longevity in humans.