The human lifespan has a natural limit and people are unlikely to live beyond about 115 years, new research suggests.
The US study found that while life expectancies have risen dramatically in the last century, the increase has been only minimal for the very old.
Their conclusions published in the journal Nature were made by analysing decades of data on human longevity.
Average life expectancy continues to increase and more people are reaching extreme old age. But, the researchers said, people who reach 110 today have no greater life expectancy than those who lived to 110 in the 1970s.
Jeanne Calment at 120: She died at age 122 having had the longest documented lifespan of any person in history. Photo: AFP
The age at death of the world's oldest person has not increased since Frenchwoman Jeanne Calment died, aged 122, in 1997.
The trend since then has been for the world's oldest person to reach around age 115, and the researchers predicted this would remain stable for the foreseeable future.
Life expectancy has been increasing since the 19th century - due to vaccines, safer childbirth and tackling killers like cancer and heart disease.
Infant and child mortality has fallen worldwide and life expectancies in developed countries now reach into the 70s and 80s.
"Despite any gains in the average life expectancy, there is a limit beyond which the maximum lifespan of humans cannot be extended," said molecular geneticist Brandon Milholland of Albert Einstein College of Medicine, who helped lead the study.
"We suspect that the accumulation of damage with age, especially mutations in the individual cells of the body, somatic mutations, ultimately places a limit on lifespan."
According to the Guinness World Records, Yisrael Kristal, at 113, is the world's oldest man. He is pictured here at home in the Israeli city of Haifa in January. Photo: AFP
Prof Jan Vijg, another of the researchers, said it was likely humans had approached the maximum lifespan.
"If you really really want to make it completely sure, you can wait for a couple more decades and you should see nobody climbs above that age ... according to the data that we now have, it's already pretty clear that's not going to happen" - Prof Jan Vijg
"For the first time in history we've been able to see this, it looks like the maximum life span - this ceiling, this barrier - is about 115.
"It's almost impossible you'll get beyond it, you need 10,000 world's like ours to end up with one individual in a given year who will live until 125 - so a very small chance."
"The odds are very slim that we will ever see a person who lives longer than Jeanne Calment," Mr Milholland said. "And if we do ... they would probably not exceed her record by very much."
Prof James Vaupel, director of the Max Planck Institute for Demographic Research, said he saw the study as a dismal travesty.
He said scientists had in the past claimed the limit was 65, 85 and 105 only to be proven wrong over and over again.
Italian woman Emma Morano, 116, is recognised as the world's oldest living person and Israeli Yisrael Kristal, 113, is the world's oldest man.
- BBC / Reuters