The Bible says God allotted 120 years to the life of man, yet few humans live that long. Seeing your 13th decade is far from impossible, though. Humans apparently are fully capable of reaching their Biblical limit — and then some.

Leandra Becerra Lumbreras of Mexico is 127 years old, or so she says. She lost her birth certificate 40 years ago. Sticking to confirmed cases, there's Jeanne Calment, who died in 1997 at the age of 122.  

If science has its way, making it to 120 may soon be less of a rarity. More importantly, living past 100 may become the norm. Humanity already gains about three months of life with each passing year. That means people born in 2014 should live, on average, a year longer than those born in 2010.

According to a newly released report from the Centers for Disease Control and Prevention, the current average lifespan in the United States is 78.8 years. (The data is for people born in 2012, the latest year researched by the CDC.) For people born in 1901, life expectancy was a measly 47.6 years for men and 50.6 for women. That’s a massive jump in just over a century. But it’s still only about three months more per year.  

As it turns out, the “three months per year” increase is steady, even without major breakthroughs. Using that rate, we can extrapolate when living to 100 will become the norm. The average American born in 2100 will likely live that long. In other words, we can be relatively confident that our great-grandkids will belong to a generation of centenarians. 

But what if there are major breakthroughs before then? What does that mean for current generations?

For current generations to reliably reach 100, we’d need to solve a single, rather odd problem: How do we get the body to keep up its natural ability to repair itself?

The body is an amazing thing, in no small part because unlike machinery, it doesn’t wear out. Not only is it constantly repairing itself, it’s also constantly renewing itself. Your body is basically brand new every seven to 10 years, according to The New York Times. Almost none of the cells that compose your organs are older than that. In fact, that’s just as true when you’re 80 as when you’re 10, according to stem biologist Jonas Frisen, who’s quoted in the Times article.

In that case, why do we age? It turns out that aging has more to do with a cell’s DNA than with the cell itself. As we get older, our cells — even our new cells — become “senescent,” and our body starts sending out “repair signals” all the time, even though no repair is needed. This leads to persistent inflammation, which is the root cause of all kinds of problems, especially the chronic problems that lead to death.

Progress is being made in the fight to overcome senescence. A drug called Rapamycin seems to help keep senescent cells from sending false repair signals. And there are at least 100 other compounds that are known to extend the lives of invertebrates. The problem is that researchers don’t know if these effects, which apply to animals like mice, will also apply to humans.

Jeanne CalmentThe key to longevity

For most of us, the science may not catch up in time, so we’re left wondering why some men and women live such inordinately long lives. What did Calment (left) and Leandra Lumbreras do right that most people don’t?

These are notoriously difficult questions to answer. The fact is, lifestyle studies of centenarians are rather puzzling. No single characteristic seems to explain their longevity. They aren’t all vegetarians, for instance — in fact, few are. They haven’t all avoided smoking or red meat. They seem to drink a bit less than your average person, but otherwise, they behave like the rest of us.

We do know that one reason life expectancy keeps growing is that death rates from serious illnesses — such as cancer, stroke, chronic lower respiratory diseases and heart disease — keep dropping.

So although there’s no Fountain of Youth, it looks like we can eat right, exercise, stop smoking, see our doctors — all the stuff that will help us stay healthy — until science and longevity gives us a few more years.

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Calment photo: Gerontology Research Group