Human life expectancy increases at a rate of about two years per decade — or roughly five hours a day. Some scientists think it's possible to live for 500 or even 1,000 years. But if we could live that long, would we want to?
In his book, Long For This World, Jonathan Weiner, 56, explores the possibilities for immortality. He tells NPR's Neal Conan that many gerontologists — specialists who study aging — hate the word immortality.
"It suggests this kind of supernatural aura that goes all the way back to Adam and Eve," he says.
Still, Weiner says many mainstream gerontologists are talking about work that's essentially the same as those on the fringe who embrace the term.
"From where I sit, it's very similar," he says.
Weiner says experts inside and outside the mainstream are asking themselves the same questions: How long do we want to live? How long is it possible to live? How long should we live?
Weiner's main character, gerontologist Aubrey de Grey, is also asking those questions. The author describes De Grey as "a youngish Methuselah" who is "at the edges of this enterprise, trying to defeat aging." De Grey thinks the many-headed Hydra of aging, where each head is a late-onset disease, can be defeated one head at a time. Weiner says De Grey believes "if we could live in the state of health that we had at, say, 12 years old, then we would have lifespans of a thousand, or more — even a million — years."
All the same, Weiner admits that short of very futuristic scenarios, death will never be cured.
"We're always going to be up against the truck that comes whizzing down the street," he says.
According to Weiner, the goal is to emulate the actual hydra, not the mythical one.
"It continually restores itself with its stem cells," he says, so "it's immortal in the sense that it's no more likely to die at a week old or two weeks old or two years old, than it was at one day old. It's aging negligibly."
Of course, if the pond dries up, the hydra dies. Weiner says that until then, it's "functionally immortal." So, biologists ask, why don't we do that? Why do our bodies stop renewing themselves after about the age of 12?
Weiner says the answer to that question lies in evolutionary biology.
"It was important for us to build sturdy bodies that will last until we reach the age of reproduction," he says.
According to Weiner, you're on the upswing until about the age of 20. After that, once you pass the age of reproduction and young parenthood, he says, "evolution by natural selection really ignores you. You're disposable, in some sense, because you've passed on your genes."
Weiner says that's why "we aren't built to last."
So, what is possible? In the foreseeable future Weiner says we could gain extra decades — good decades — of life without disease and infirmity.
Weiner says that many people around his age are starting to consider what to do with all that extra time.
"Since we have a longer lifespan, and a longer healthy life expectancy," he says, "maybe we can add another chapter."
According to Weiner, that attitude is bound to get more popular as life expectancies increase.