Human beings have a maximum lifespan, and it's probably 115 years, researchers said Wednesday.
While life expectancy continues to increase — that's a measure of how long any individual can expect to live — maximum lifespan has not, the team at the Einstein College of Medicine in New York found.
And it probably won't, they predict.
"Our data strongly suggest that the duration of life is limited," Jan Vijg and colleagues wrote in their report, published in the journal Nature. "Our data seem to say it is really around 115," Vijg added in an interview.
Vijg is a professor of genetics, but he used simple statistics to come up with his conclusion.
Jeanne Calment set the absolute record for long life. She died when she was 122, in 1997. Since then, no one has lived any longer.
Vijg's team looked at global databases on lifespan and found it peaks at around 100 and then falls back down again. The limit seems to be about 115, or 125 if you account for the very occasional outlier, like Calment.
"We show that improvements in survival with age tend to decline after age 100, and that the age at death of the world's oldest person has not increased since the 1990s. Our results strongly suggest that the maximum lifespan of humans is fixed and subject to natural constraints," they wrote.
This is not the same thing as improvements in life expectancy, which soared after antibiotics, vaccines and other medical breakthroughs got rid of diseases that kill people when they are young. Even under perfect conditions without disease, everything dies eventually.
And it's not that there is some genetic time bomb, but more that the mechanisms for keeping the body going wear out.
It's not a particularly new idea, but the data had not been there to back it up. Now that countries around the world are keeping careful records, Vijg said, it's possible to prove it.
Related: Want to be 105? Check Your Genes
"Biologists always strongly suspected that maximum lifespan was genetically determined and specific to the species," he told NBC News.
"A mouse in the wild doesn't live more than seven, eight months or so. But if you take those mice and keep them in captivity and optimal conditions, they die when they are two years old or so. But they die. And that is because of the aging process."
Dr. Thomas Perls of Boston Medical Center and the Boston University School of Medicine agrees.
"This is all stuff many of us in the field knew. It was just a matter of putting it down on paper," Perls told NBC News.
Related: Oldest Man in History Dies at 116
Perls is studying so-called super-agers — people who live to be 110 or older.
"We now have 150 people over 110. They are very, very rare," Perls said.
He calculates that one in 5 million people lives to be 110 or older. He thinks there is something different about them.
It's easy to get to be old, Perls says.
"That is what the Seventh Day Adventist health study has shown us," he said.
"If you take advantage of this average set of genes that we have — you don't smoke, you don't drink, you get regular exercise, you have a vegetarian diet, you're not overweight and maybe you do things to manage stress well, then you do what Seventh Day Adventists have, which is you have an average life expectancy of 89 if you are a woman, and 86 if you are a man."
But to become super-old, it looks like you need a unique set of genes, he said.
"These incredibly rare ages that approach the limits of lifespan — 70 to 80 percent of it is explained by a difference in genes and not so much health behaviors."
He's identified more than 100 genes involved in healthy aging.
Related: Healthy Diet May Reverse Aging
"It is not a single gene. It is many, many genes, each with modest effect. It's kind of like winning the lottery. Getting one or two numbers is not rare. Getting seven is rare," Perls said.
David Sinclair, a pathologist at Harvard Medical School who also studies aging, disagrees that there's a set limit to lifespan. He's been working for decades on various compounds that can reverse the aging process in cells.
"Aging reversal is becoming commonplace in labs, including my own," Sinclair told NBC News.
"We were able a couple of years ago to show we could reverse aging in mice within a week."
He's been trying to do the same in humans, with mixed results. One company he set up to develop age-reversing compounds was closed by its big pharma owner, GlaxoSmithKline, in 2013. But Sinclair says the company is continuing the research internally and argues there are no set limits. He doesn't believe that looking at past patterns can predict the future.
"There are many species that live longer than us," he said. "A bowhead whale lives to more than 200."
Nijg doesn't disagree that drugs may help some people live longer than they normally would, and not just by treating age-related diseases.
He points to studies on the diabetes drug metformin and the immune suppressant drug rapamycin, which suggest the drugs might slow some aging processes.
"They won't break through the ceiling," Vijg said. "But if it can get me another 10 years in great health, I'll take it."