When your mother said you could grow up to be president someday, she probably didn’t think you’d set your sights on ’08–3008, that is. A spry 1000-year-old in the Oval Office might sound fantastical, but at least one scientist in the longevity field thinks that, if we can maintain our aging bodies as if we were a healthy 35, living for millennia should be within our grasp.
Many researchers who study aging hope that they might one day devise interventions that will help us celebrate copious birthdays. So far, they have boosted life span sixfold in worms and 50% in rodents. These successes have led some researchers to speculate about how far it might be possible to go. Although many think that we should be able to hit 120 to 130 years, one researcher believes we will get stuck at 88, and another can see us living to 5000.
For a long time, scientists thought that even though life expectancy–the average time that we can expect to live–has gotten longer with each passing decade, there exists some age past which humans just couldn’t live–the life span equivalent of the 4-minute mile. But the notion of a strict biological limit has fallen out of favor.
“This whole idea that there’s a wall came from people spouting stuff off the top of their head,” says evolutionary zoologist Steven Austad of the University of Texas Health Science Center in San Antonio. What’s more, the notion of a limit goes against evolutionary theory: The forces that optimize an organism’s fitness stop operating after that creature has raised its young. So, Austad says, natural selection would have no reason to favor the evolution of a grim reaper gene that would switch on and kill an organism that’s past its prime.
Of course, the absence of a strictly enforced limit does not mean that organisms can live forever. Entomologist-turned-biodemographer James Carey of the University of California, Davis, says that measuring longevity in 6 million fruit flies has taught him that life span hinges on a series of confounding variables. Predicting life span, he says, is like estimating how far a bird can fly. The answer depends on whether the birds are allowed to rest or if they encounter a tail wind. “But clearly,” he says, “they’re not going to fly to infinity.”
For humans, some of the confounding variables are obvious, such as access to food or adequate health care. Others are surprising. For example, actors who win Oscars live longer than those who are simply nominated. “All the people in the Academy Awards could probably win: It’s almost a flip of the coin. But something magical happens to the individual because he won,” says Carey, although no one knows what.
