No one might ever challenge the 122-year record of the longest-living person in documented history, said a study which claimed to have found a "ceiling" to maximum human lifespan.
Sifting through demographic data from more than 40 countries around the world, New York-based researchers found that an end to the long-running rise in maximum lifespan "has already been attained," in the 1990s.
The plateau was reached in about 1997 -- the year that Frenchwoman Jeanne Calment died at the unbeaten age of 122 years and 164 days.
"The trend since then has been for the oldest person in the world to be around 115 years old," study co-author Brandon Milholland of the Albert Einstein College of Medicine told AFP.
This was despite average life expectancy continuing to increase as medical care, nutrition and living conditions improved.
In other words, more people are living into old age these days, but exceptionally long-lived individuals were not getting quite as old as before.
"We predict this (trend) will remain stable for the foreseeable future," said Milholland.
"It is possible that someone might live slightly longer (than 115) but the odds of anybody in the world surviving to 125 in any given year is less than one in 10,000."
This could all be changed, of course, by a major medical or technological breakthrough -- the long-sought elixir of life.
"We can't eliminate the possibility of a breakthrough that will further extend lifespan, but it would have to be unlike anything seen before," Milholland said.
"The medical advances of the past few decades may have increased life expectancy and quality of life, but they have not done anything to increase the maximum lifespan."
- Natural limit -
Lifespan is the term used to describe how long an individual lives, while maximum lifespan is the age reached by the longest-lived member of a species.
Life expectancy is the average duration of life that individuals in an age group can expect to have -- a measure of societal wellbeing.
According to the researchers, life expectancy globally has risen almost continuously since the 19th century.
Babies born in the United States today, for example, can expect to live to nearly 79 compared to 47 for Americans born in 1900.
Since the 1970s, maximum life expectancy has also risen, but seems now to have reached a plateau.
This suggests there may be a biological limit to human lifespan -- despite the hope some people may hold out for finding the fountain of youth.
"Our results strongly suggest that the maximum lifespan of humans is fixed and subject to natural constraints," wrote the team.
Milholland admitted having been "a little bit" disappointed by the findings.
However, "as scientists, our duty is to the truth, even if it is not entirely pleasant," he said.
"I predict that those who seek immortality will still cling to the hope of some undiscovered technology that will allow us to exceed the limit we found.
"In a sense, we have done them a favour; if they had placed their hopes on conventional medical advances, which we have found do not have an effect on lifespan, they would have been sorely disappointed."
Commenting on the study, Stuart Jay Olshansky of the University of Illinois, Chicago, wrote in Nature it was a reminder that "humanity is approaching a natural limit to life."