Given these statistics, you can be sure that the record for the longest lifespan will also increase. Yet nearly a quarter of a century after Calment's death, no one is known to have reached or exceeded her 122 years. The next was an American named Sarah Knauss, who died two years after Calment at the age of 119. The oldest living person is Kane Tanaka (118), who lives in Fukuoka, Japan. Very few people make it past 115. (Some researchers have even questioned whether Calment really lived as long as they claimed, though most accept her records as legitimate based on the weight of the biographical evidence.)
As the world population approaches eight billion and science discovers increasingly promising ways to slow or reverse aging in the laboratory, the question of the potential limits of human life expectancy is more pressing than ever. When their work is closely examined, it is clear that longevity scientists have a wide range of nuanced perspectives on the future of humanity. Historically, however, and somewhat recklessly in the opinion of many researchers, their views have been divided into two broad camps that some journalists and researchers have labeled pessimists and optimists. Those in the first group consider lifespan to be a candle wick that can only burn for so long. They generally think that we are rapidly approaching or have already reached life expectancy and that soon we will not see anyone older than Calment.
In contrast, the optimists see the lifespan as a highly, perhaps even infinitely elastic band. They anticipate a significant increase in life expectancy around the world, an increase in the number of extraordinarily long-lived people – and eventually supercenturies who survive Calment and push the record to 125, 150, 200 and beyond. Though unresolved, the longstanding debate has already led to a much deeper understanding of what defines and limits lifespan – and the interventions that could one day extend it significantly.
The theoretical limits the length of a human life has annoyed scientists and philosophers for thousands of years, but for most of history their discussions have been largely based on deliberation and personal observation. In 1825, however, the British actuary Benjamin Gompertz published a new mathematical model of mortality that showed that the risk of death increased exponentially with age. If this risk accelerated further over the course of life, people would eventually reach a point where they essentially had no chance of surviving until the next year. In other words, they would reach an effective life limit.
Instead, Gompertz found that the risk of death was on a plateau with old age. "The lifespan limit is an issue that is likely to never be determined," he wrote, "even if it should exist." Since then, other scientists around the world, using new data and more sophisticated math, have found further evidence of accelerating death rates, followed by death plateaus not only in humans but also in numerous other species, including rats, mice, shrimp, nematodes, and fruit flies and beetles .
A particularly provocative study in the prestigious research journal Nature in 2016 strongly suggested that the authors had found the limit of human lifespan. Jan Vijg, geneticist at Albert Einstein College of Medicine, and two colleagues analyzed decades of mortality data from several countries and concluded that the highest reported age of death in these countries rose rapidly between the 1970s and 1990s, but has failed to rise since then and stagnates at an average of 114.9 years. The human lifespan seemed to have reached its limit. Although some individuals, like Jeanne Calment, could live to an astounding age, they were outliers and not indicators of continuous life extension.