With the development of rejuvenation therapies underway, and accelerating, somewhere ahead lies a dividing line. Some people will be the last to age to death, too comprehensively damaged for the technologies of the time to recover. Everyone else will live indefinitely in youth and health, protected from aging by periodic repair of the underlying cell and tissue damage that causes dysfunction and disease. Where is that dividing line? No one can say in certainty. I look at the children of today, with long lives ahead of them, and find it hard to believe that in a hundred years the problem won't be solved well in time for them to live for as long as they choose. Equally, people in middle age today will certainly benefit greatly from the advent of first generation rejuvenation technologies, such as senolytics, each narrowly focused on one mechanism of aging. Yet I'm skeptical that matters will progress rapidly enough to rescue them. So somewhere between those two points are the people on the very edge; the last mortals.
In a sense this isn't terribly profound at all. It is the same story for every as yet uncontrolled medical condition, where the medical research community is working towards effective treatments that will arrive at some uncertain future date. There will be those who are the last to die, just as the therapies that save everyone else are rolling out. It is only the magnitude that is greater in the case of aging - a hundred or a thousand times greater. Does the fact that it affects everyone mean that there will be public disorder, disputes between the first immortals and the last mortals, where only private, personal existential crises exist today? I think claims of societal unrest as a result of the realization that your children will live indefinitely, while you yourself will not, are likely overwrought.
Ever-growing lifespans are the result of regular advances in medical science. In 1900 the three leading causes of death in the United States were pneumonia/influenza, tuberculosis, and diarrhoea. Only a century and a bit on, many of the major acute illnesses are tractable. Every month brings striking new medical advances. Increasingly, medical research is shifting from acute conditions such as influenza towards chronic conditions including diabetes and Alzheimer's. Ageing is the ultimate chronic condition, and there seems to be no reason, in principle at least, that would prevent us from discovering a means of halting or reversing ageing itself.
What if that all happens sooner rather than later? But what if it's not soon enough? Imagine that, after a few more breakthroughs, a scientific consensus emerges that we will have conquered illness and ageing by the year 2119; anyone alive in 2119 is likely to live for centuries, even millennia. You and I are very unlikely to make it to 2119. But we are likely to make it relatively close to that date - in fact, relative to the span of human history, we've already made it very close right now. Think that through, carefully. What would it mean to realize that you very nearly got to live forever, but didn't? What would it mean if, in our looming senescence, we were increasingly forced to share social space with young people whose anticipated allotment of time massively dwarfs our own? We would then be the last mortals.
To be precise, the kind of immortality I have in mind can be called biological immortality. A biologically immortal organism does not die from illness or ageing - though they may still die in a plane crash. If humans acquired biological immortality, our expected lifespans would jump to enormous lengths. Almost everyone would still eventually die; statistics dictate that if you fly on planes every few weeks for eternity, eventually one will crash. This point allows us to sidestep one of the perennial questions about immortality: is endless life something we'd really want? What is distinctive for biological immortals is that death becomes only a possibility, an option, not an inevitability on a fixed timetable. This sort of immortality, I would think, is definitely not a curse. To have the option of living healthily a very long time, possibly for as long as one could want (but no longer), seems like an unmitigated blessing.
Until now, the wish for immortality was mere fantasy. No one has ever lived beyond 122 years, and no one has reasonably expected to do so. But what happens once the scientists tell us that we're drawing near, that biological immortality will be ready in a generation or two - then what? Seneca told us to meet death cheerfully, because death is "demanded of us by circumstances" and cannot be controlled. Death's inevitability is what makes it unreasonable to trouble oneself. Yet, as I've been arguing, soon death may cease to be inevitable. It may become an option rather than a giver of orders. And, as the fantasy of immortality becomes a reasonable desire, this will generate not only new sorts of failed desires, but also new ways to become profoundly envious.