James' World 2

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A few years ago, I wrote a memorable and quite controversial story about Jeanne Calment, who was then – and remains now – the official holder of the world longevity record. She was born in 1875 and died in 1997, aged 122 years and 164 days. At least that’s the official version of events. According to some doubters, the woman who died as Jeanne Calment was actually her daughter Yvonne, who fraudulently assumed her mother’s identity when Jeanne died in 1934. Yvonne was 23 years Jeanne’s junior. Still a good innings, but not a record-breaking one.

The matter remains unresolved, and so, for now, Calment remains one of the most important data points in biogerontology. When we ask, “how long can a person live?”, the answer is “at least 122 years and 164 days” – assuming Jeanne Calment really did live that long.

Whether a person could live longer has long troubled scientists. It’s an important question in biogerontology because, if we want to achieve life extension, we need to know what we’re aiming for. But it’s surprisingly hard to answer. Calment is an outlier: nobody else has reached 120, which is one reason for the suspicion. The second-longest-lived person was Kane Tanaka, who racked up 119 years and 107 days, and the oldest person today has just turned 117. Aside from a few mavericks, however, everyone agrees that there is a natural limit.

But where is it? There are two main ways of tackling this question. One is by studying demographic data on verified supercentenarians. One such frequently cited analysis produced an estimate of roughly 115, but did not rule out somebody living to 125. Another concluded that Calment’s record is likely to be broken fairly soon.

Another approach is by computer modelling. One such model analysed short-term fluctuations in red and white blood cell counts in adults aged 85 and over, which the researchers converted into a measure of their resilience to terminal age-related disease. At some point, resilience breaks down completely, marking the point of no return. The researchers concluded that this varies from person to person, usually kicking in at about 120. But even for the most resilient individuals, there is a hard upper limit of 150.

There’s a big difference between 125 and 150, and we’ll get onto this. But one thing these studies don’t take into account is future advances in medicine. In the 1920s, scientists believed that it was impossible to live past 105, according to biogerontologist Richard Faragher at the University of Brighton, UK. But over the following century, medical breakthroughs steadily added years to people’s life expectancies, helping (along with better nutrition and sanitation) to nudge the longevity record upwards.

What happens if that trend continues? To find out, a team at the Skolkovo Institute of Science and Technology and the Artificial Intelligence Research Institute, both in Moscow, Russia, ran a thought experiment. Imagine, they said, that we manage to cure all the theoretically curable causes of ageing. The only unfixable one is damage to the DNA in our cells, which accumulates remorselessly as we age. In that scenario, the upper limit of a human life soars to 194 years.

I’ll stick my neck out and say it ain’t going to happen in my lifetime, and also point out that the causes of ageing are not yet fully understood. Even so, it suggests there’s quite a lot of room for improvement.

But back to the real world. Why do upper age estimates vary so much? Re-enter Jeanne Calment. When I was reporting that story, I spoke to a longevity researcher called Saul Newman, then at the Australian National University in Canberra. He had just published a paper showing that a small number of errors or fraudulent entries in paper records such as birth certificates can significantly distort longevity data. He told me he suspected the Calments’ alleged identity fraud was just the tip of the iceberg.

Newman, now at the University of Oxford, has just published a book, Morbid: Debunking modern longevity science, revealing the shocking extent of those errors and frauds. In Greece, for example, around 70 per cent of centenarians were found to be dead, kept alive on paper so their relatives could keep on drawing their pensions. Even higher levels of pension fraud were discovered in Japan. People have historically inflated their age for many other reasons, to join (or dodge) military service, get married or get a job. Clerical errors are rife too, especially from the time when today’s centenarians and supercentenarians were born.

These errors inevitably feed into estimates of the upper limit of human longevity. If the demographic data used as an input is riddled with inflated ages, the output is probably also inflated. Garbage in, garbage out. People used in modelling studies are also tagged with an age, which could well be wrong. When the journal Nature asked Newman where this leaves the debate about a maximum human lifespan, he answered: “in an absolute shambles.”

When I was researching the Calment story, I also came across a 2011 paper that found that, across the whole world, 98 per cent of claims of lifespans over 115 could not be verified. The same paper also found that, in countries with rigorous birth records going back more than 150 years, not one person has been proved to have lived past 115. That, I think, is the best estimate we’ve got. Five score years and fifteen. I’m halfway there.

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