Birth Of A Science
In the next installment of Immortality: A User's Guide—a paradigm shift in our understanding of why we age.
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In the opening installment of this series, I told the story of Jeanne Calment, generally considered to be the longest-lived person in recorded history. The fact that I am slightly obsessed with Calment’s story will not come as a surprise to most of you, given the work I did writing and producing the book and TV series Extra Life. That project was mostly a look backwards at the last century of health progress, anchored in one under-celebrated fact: since the end of the Great Influenza a hundred years ago, we have doubled global life expectancy. In 1920, the average human being could expect to live 35 years. Today, that number is 70.
At first glance, that story of doubling life expectancy would seem to support the idea that we can push past the Calment boundary: that we’re all going to be living to 120 and beyond in our near future. The upward slope of expected life has been remarkably steady over the past century (though it has dipped for the first time with the COVID pandemic.) For the Calment boundary to be surpassable, you don’t need any radical change in outcomes; you just need that upward slope of extended life to continue in a linear fashion. If life expectancy keeps increasing at a steady rate, the global norm will be 120 sometime in the second half of the 21st century. And that would be the average lifespan. Many people would live much longer lives.
But there’s something misleading about this life expectancy history. Much of the progress we made this past century came from reducing infant and child mortality. The big driver was not old people living longer lives; it was children not dying. Up until the 20th century, a third of all children died before reaching adulthood. When overall life expectancy was 35, that didn’t mean that everyone dropped dead before reaching 40. Many people lived into their 70s or 80s. It’s just that a massive section of the population died six days into their life, or six years. Those childhood deaths pulled the average down.
But it’s also true we have made meaningful advances at the other end of the aging process. Demographers talk about expected life at different ages: expected life at birth versus expected life at, say, 20. In the old days, when childhood was so dangerous, your expected life at 20 was much higher than your expected life at birth. In the middle of the 19th-century, the average English person who made it through childhood could expect to live a total of 60 years. Today that number is 85. If you project that trend forward, you get to a less dramatic outcome, with average life expectancy reaching 100 sometime in the second half of this century. Good news, certainly, but not exactly a radical breakthrough.
And there’s another factor to consider when thinking about the future of lifespan, which is the idea of an outer boundary. It is possible that we could slowly and steadily decrease everyone’s mortality, until the average person lives to 100. But at the same time, it might prove to be impossible to break through the Calment boundary. It’s been a quarter of a century since Jeanne Calment died, after all, and as far as we know, she still holds the record for total lifespan.
The limits of human lifespan have actually been the subject of very heated scholarly debate over the past few years. A controversial 2016 paper concluded that after decades of increases, we seem to have hit a wall in the 1990s at around 115 years. Since that time, it has gotten much easier to live to 100. (According to some accounts, centenarians are actually the fastest growing age cohort in the United States right now.) But getting to the Calment boundary — or better yet, exceeding it — remains an impossibility.
Now, not everyone agrees with the conclusions of that 2016 paper. In fact, there’s a wonderful public bet between two scientists over the question of whether the first person to live to 150 is alive right now. (They’ve agreed to determine a winner in the year 2150.) But I think the data makes one thing clear: for us to reach the Calment boundary — where the average life expectancy is a 120 or beyond — we won’t be able to rely on the general approach that led to such dramatic progress in the preceding century. We’re going to need a paradigm shift. And as it happens, a number of very smart people think we are right in the middle of one.
When you look at the history of science, some paradigm shifts come about when people discover a new explanation or solution to an existing problem. Take a disease like cholera, for instance—one of the great killers of the 19th-century, and the centerpiece of my book The Ghost Map. Scientists and physicians knew that cholera was a problem that needed to be solved, but they didn’t understand what was causing cholera in the first place. They thought it was a disease caused by something transmitted through the air. But after some pioneering detective work from the London doctor John Snow in 1854, it was revealed that cholera was in fact a waterborne disease—one of many it turned out. And that led to a revolution in cleaning up the water supplies of big cities: building sewers, chlorinating drinking water. That paradigm shift was a major driver of the life expectancy increase of the 20th century. But the problem Snow was originally trying to solve—how to stop people from dying from diseases like cholera—had been defined long before Snow started his investigation.
But some paradigm shifts are even more radical. Sometimes they involve the discovery of an entirely new problem. Something that had always just been taken for granted—largely ignored by the scientific community—suddenly becomes an urgent mystery, a phenomenon that requires explanation. My book The Invention Of Air tells the story of one such conceptual shift: the discovery that air itself was made of something, something that could be analyzed and measured by chemistry. We happen to be living through a comparable paradigm shift right now, one that has been slowly unfolding over the past three decades. At its core is a profound question about our existence: Why do we age at all?
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