In one new paper
, Dutch scientists predict that, by 2070, our lifespan may increase to 125 years while beyond that, the sky may be the limit. Their analysis was published Wednesday in the journal Nature.
The debate over his original paper
, published last October in Nature and widely reported by CNN
and other media outlets, took Jan Vijg, senior author, by surprise.
For a biologist, a natural limit to the lifespan "makes a lot of sense, so that's why I never imagined the paper would stir up so much comment," said Vijg, a professor at Albert Einstein College of Medicine in New York.
To prove a 125-year lifespan is possible, researchers from the Netherlands Interdisciplinary Demographic Institute team began their study by refuting the relationship between age and immortality posed by Benjamin Gompertz
This 19th-century mathematician pored over mortality data and noticed that young people have a very low chance of dying. Yet, in middle age, the chance of dying increases and then rises again dramatically in old age.
This exponential increase in the rate of human mortality has long been accepted wisdom, yet the Dutch researchers decided to challenge it. Instead of basing their work on data derived from the general population, they used data from a group of people noted for their long lives -- Japanese women.
Using mathematical models, they claim mortality goes down in old age and projected an astounding new human lifespan -- 125 years -- will be achieved by 2070.
Along with this theory, an additional four separate papers poke holes in Vijg's work. A Canadian team
of scientists claims Vijg's original paper is based on statistically "noisy" (or meaningless) data. Meanwhile, a research team from the University of Copenhagen
argues that any inferences about lifespan potential are premature; a team from the Max Planck Institute
claims there's simply no evidence of a "looming limit;" and a team from the University of Groningen
offers four cohesive arguments contesting the conclusions drawn by Vijg's team.
What inspired this heated debate?
In their paper, Vijg and his graduate students, Xiao Dong and Brandon Milholland, analyzed aging trends in the United States, the United Kingdom, France and Japan.
Vijg explained that their analysis was based not on some mathematical model that projected future data, but on "actual data" of real human lives. They examined not one but two different data sets, and what they observed was that, despite life expectancy being dramatically higher than it was 100 years ago, the probability of anyone living for more than 125 years was unlikely.
"Initially, you see this increase every year and you see this oldest record holder until the 1990s, and then it stops," said Vijg. "Think about it, how strange it is."
The number of healthy centenarians increased dramatically every year. That being the case, Vijg theorized "the supply is certainly there" to create more record-breakers, every year, yet there were none.
Vijg wondered, "How is that possible?" A decades-long plateau following years of new old-age records must mean humans have reached the lifespan limit, he and his colleagues concluded.
It is a rather logical conclusion for biologists, who have long seen that individual animal species each have a particular span of time in which they are born, develop into maturity, and then die, Vijg explained.
"When Jeanne Calment
died, I really thought that this was the beginning of something very dramatic," said Vijg. Jeanne Calment died in 1997 at age 122, which remains "the greatest fully authenticated age to which any human has ever lived," according to Guinness World Records
Hearing about Calment's long life, Vijg rebelled against the accepted wisdom that lifespan "must be fixed, it must be like a ceiling."
Yet, testing the theory, Vijg and his co-authors found no fresh old-age record breakers. Sure, the Canadian scientists who created a mathematical model found random plateaus, some seven years long -- but still their research fails to explain a plateau of decades, said Vijg.
The Canadian scientists may believe their research disproves his, but instead, it "is a beautiful confirmation of what we found," he said.
"They want us to be wrong," said Vijg, who with his colleagues published a rebuttal
to all the criticism. "I can see that it's very depressing when you find out that we can never get older than 115 years on average."
Vijg, though, is not a depressed man.
He says he's seen the tremendous strides made in all scientific fields as well as technology and hopes that someday the aging process might be halted.
"We may be able to do that at some point, as I say, by the way, at the end of my paper," said Vijg. "But if we are not able to do that because aging turns out to be still very mysterious, or a process that we cannot really intervene with, then we are stuck with a real maximum lifespan that fluctuates around 115."
"Accept it," he says.