Smell of Death
Earlier studies had showed that restricting flies' diets could change their death rates rapidly, which led scientists to suspect that smell was playing an important role.
"Once they started [eating] healthily, their mortality rates dropped within a day," Pletcher said. "This was sort of striking and showed they could adapt to their environment very quickly."
Oddly, it's as though the flies' brains don't listen to their stomachs, he added. Instead, the animals rely mostly on smell to tell them how much food is available.
In the new study, mutant flies with damaged sniffers lived longer regardless of their diet and also escaped the ill effects of smelling food. In fact, these flies lived about 75 days—the longest of all.
But it's not yet clear what the new findings might mean for people, Pletcher said. (Related: "Happy 120th? Science Pushes Human Longevity" [October 20, 2005].)
The study also illustrates how aging is not just an inevitable decline and breakdown.
Instead, animals can subtly and unconsciously control how fast they age depending on what they see—or smell—is happening in the environment.
The new study didn't find any strong link between life span and the number of eggs that the flies produced.
But living longer might still be affecting their reproduction, said Daniel Promislow, a geneticist at the University of Georgia in Athens.
Often these differences only show up in stressful conditions, which weren't explored in the new study, Promislow said.
"The flies may lay fewer eggs under stressful conditions," he added. "Or there may be some other tradeoff. The quality of the eggs that they lay can be lower."
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