They recorded lifespans of flies raised on different diets and at high and low temperatures. They also evaluated how exposure to heat shock and starvation stress influenced longevity. Ten of the mutations caused some flies to live longer and others to die sooner. The researchers used as an example one gene variation that extended females' lives if the flies survived a hot spell early in life, but caused earlier deaths if the flies lived at a constant room temperature. Male flies with the same genetic variation, exposed to the same environment, experienced no change in longevity.
Different researchers get different answers.
One might wonder if the environment accounts for some of these disparities. A different study at the University of Minnesota in St Paul found environmental or gender differences had little effect on longevity-associated genetic variations. But an Italian study found a genetic variation that makes men but not women live longer. Mackay said studies of other animals, including humans, shows that environment and gender alter the effects of genes. She recommends further research, using different strains, to determine if the results can be generalized.