Immortality: How Many Years Can A Healthy Human Live On Earth?

The question of whether there is a maximum lifespan for healthy humans has split experts for decades. 

The world's oldest human, who passed away at the age of 118 some weeks back, has resurrected this discussion.

According to Guinness World Records, Spanish great-grandmother Maria Branyas Morera, 115, took up the title of the oldest living person after French nun Lucile Randon passed away on January 17, 2023.

A human might theoretically live for up to 100 years without experiencing an accident or disease, according to a theory put forth by French naturalist Georges-Louis Leclerc, also known as the Comte de Buffon, back in the 18th century.

Since then, improvements in living standards and medical technology have pushed the upper limit back a few decades.

Jeanne Calment, a Frenchwoman, turned 120 years old in 1995, marking a new milestone.

At the age of 122, Calment passed away two years later. She is still the oldest person to have ever lived, at least according to verification.

In 2021, there were reportedly 593,000 persons who were 100 years of age or older, up from 353,000 a decade earlier, according to the United Nations.

Over the following ten years, the Statista data agency predicts that the number of centenarians will more than double.

Another factor that might have astonished the Comte de Buffon was the emergence of supercentenarians, or those who are 110 years of age or older, whose numbers have been rising since the 1980s.

How Long Can A Healthy Human Live?

Some scientists contend that there are stringent biological limitations on our species' ability to live long lives.

Human longevity has not increased since the late 1990s, according to geneticists who published their findings in the journal Nature in 2016.

Even though there were older individuals in the world, they discovered after analyzing demographic data from around the world that the average human lifespan has decreased after Calment's passing.

"They concluded that human lifespan has a natural limit and that longevity is limited to around 115 years," French demographer Jean-Marie Robine explain in his journal.

"But this hypothesis is partly disputed by many demographers," said Robine, a specialist in centenarians at the INSERM medical research institute.

"Research in 2018 found that while the rate of death increases with age, it slows down after 85.

"Around the age of 107, the rate of death peaks at 50-60 per cent every year, the research said.

"Under this theory, if there are 12 people aged 110, six will survive to be 111, three to be 112, and so on," Robine explained in his Journal.

Supercentenarians and the Numbers of Game

However, the more supercentenarians there are, the greater the likelihood that a select few may live to record ages.

If there are 100 supercentenarians, "50 will live to be 111 years old, 25 to 112," Robine argued.

"Thanks to a 'volume effect', there are no longer fixed limits to longevity."

The window, however, is getting even smaller as a result of research that Robine and his team plan to publish this year that demonstrates how the death rate increases after age 105.

Does this imply that the number of years we can live is fixed? That is too far for even Robine to go.

"We will continue to make discoveries, as we always have, and little by little the health of the oldest people will improve," he wrote.

Other experts are also cautious about choosing a side.

"There is no definitive answer for the moment," said France Mesle, a demographer at the French institute of demographic studies (INED).

"Even if they are increasing, the number of people reaching very old age is still quite small and we still cannot make any significant statistical estimate," she argued on her part.

So, it might be necessary to wait till there are more supercentenarians before testing the "volume effect".

Of fact, some medical advances in the future could quickly change what we know about death.

A French physician with a focus on the elderly named Eric Boulanger said that "genetic alteration" could enable some people to live for 140 or even 150 years.