A century ago the odds are I would be dead by now.
For every hundred people born somewhat more than half made it to adulthood. Now almost all of us do.
And while a European aristocrat might expect to live into their sixties, ordinary working people were more likely to die in their forties, used up by a life of labour, literal or figurative.
Even those lifespans were an improvement on what had gone before: at the start of the scientific revolution in the sixteen-hundreds, the average lifespan for both the high and the low was more-or-less the same as it had been for the past ten thousand years.
But what is the "average lifespan"? Infant mortality skews the figure badly if we just take the average of all deaths, but this is the figure most often quoted. It's useful precisely because it folds infant mortality into the measure, but it doesn't necessarily give us a good sense of when people died.
Expected lifespan at the age of 20 is another common measure, as is age of death for adults.
All these measures point to a similar picture in the pre-modern world: an overall lifespan of about 35 years, including infant mortality, and an age at death for aristocratic adults that was around 50, rising slowly during the Middle Ages and Early Modern period from about 48 to 54 in England and Wales. That's a ten percent increase in a thousand years, for the nobility. Other measures suggest averages as low as 42 years for nobility, and likely lower still for commoners.
And if we look even further back in time we find among modern hunter-gatherer populations, who are still living as people did before the agricultural revolution, that things were pretty similar: if you made it to 15 or 20, you were likely to die peacefully in your sleep in your early 40s, although death in childbirth (for women) and death by violence (for men) were both also quite common.
Today, the most common age of death in Britain is 86 for men, 88 for women, with the majority of that gain having come in the past century, and all of the rest in the 200 hundred years before that.
What happened?
There are at least two related threads: one is we started learning things that allowed us to cure the conditions and causes of death, both socially and medically. The other is we started to care.
There's a question of which came first, the cure or the care. Maybe knowing we didn't have to accept our fate made caring easier. Maybe the nascent individualism of the Protestant revolution made people less willing to go quietly into that good night. Maybe the two phenomena worked together.
My own unbiased perspective is that the discovery of probability in the 1600s was the watershed moment between the Modern world and everything that went before: natural philosophers started to measure the distributions of phenomena, and to invent ways to analyze and manipulate those distributions to get insight into the underlying causes of the differences they observed between distributions over time or space.
While Galileo and his successors opened up the vast depths of space using telescopes, and Robert Hooke and others used compound microscopes to open up the world of the very small, probability theory allowed us to bring the rare and complex within the scope of our limited understanding.
Probability is the telescope of the mind.
Using newly conceived ideas of probability, physicians started to look at how long people lived in different places, and how long different classes of people lived. They also started to look--much more tentatively--at how likely various outcomes were when they treated a patient in different ways.
Rather than focusing on anecdotes and testimonials, they started counting things, and writing those numbers down, and publishing them in the newly-conceived vehicle of communication we now know as the scientific journal: the Philosophical Transactions of the Royal Society started publication in 1665, made possible by the invention of the printing press a century before. If we are looking for a single thing that changed everything, the printing press is probably it, as it made the dissemination of large tables of numbers possible.
It made counting things worthwhile.
Once you start counting things, you notice differences. People here lived longer. Upper class people lived (a bit) longer. Treating smallpox with variolation--which was inoculation with puss from smallpox blister--could be shown to work! It wasn't a matter of opinion any more than the number of sheep in a field was a matter of opinion.
Pretty soon a great many things were no longer a matter of opinion, or religious doctrine, or personal revelation. They became simple--or sometimes increasingly complex--questions of counting things.
Not everyone was enthused about this, and the rump of that population of opponents is still with us, and still quite vociferous, today.
But the next three hundred years saw an increasing focus, technically and socially, on the newly identified causes of death, and despite the opposition of people who fought desperately to retain their power to force their baseless, made-up, narratively-satisfying opinions on others, we started to see progress, slowly at first, but building to the explosive growth in lifespan we've seen in the past century.
Many of the gains are not due to knowledge and technology as such, but the power of ordinary people to get access to that knowledge and technology, and where there have been retrenchments in lifespan in the past decade it has been where democracy is fragile or non-existent.
Public health has been primarily the work of engineers: clean water, effective sewage collection, treatment, and disposal, and similar engineering initiatives turned cities from toxic, vermin-ridden incubators for disease to the safest, healthiest environments most of humanity had ever encountered, to the extent that there is now a debate as to whether the environment is too clean for optimal health, as we've seen a rise in allergies that may be due to lack of childhood exposure to dirt and dust and pollen and whatnot.
Investment in clean water and the like doesn't happen unless there is public demand for it, and the government is sufficiently at risk--either because it is a fragile autocracy or a functional democracy--that political power-mongers feel they have to make such investments or risk losing power.
Is there an upper limit to the human lifespan? I don't expect to live to be a hundred, but maybe my offspring will. I've seen estimates that put the ultimate average age of death in the mid-90's, given what we know about human senescence.
That, however, doesn't factor in what we're learning now about programming life's machinery, which could produce extensions that are beyond anything yet seen. If that happens, what the ultimate upper limit will be remains to be seen.
Unlike the gains we've seen in the past century, however, which drove a modest increase in inequality as the rich benefited slightly more than the poor while everyone still lived longer, the next leap in human lifespan is likely to come from individual therapies, at least in the developmental stages. But the nature of biotechnology is that it is self-reproducing. Learning how to do something for the first time is hard. Replicating the molecular machinery that allows us to do it is exceptionally easy.
Imagine an mRNA vaccine against some range of cancers, or cardiovasular disease: inventing it would be hard. Generating and packaging an mRNA sequence is easy.
Even so, there is a remaining question. Assuming we will soon have the ability to indefinitely prolong human life, why would we?
The ancient Greek philosopher Epicurus is supposed to have said, "For a wise man one lifetime is enough, and a fool wouldn't know what to do with eternity."
What will we do with our vastly extended lifespans that make them worthwhile?
What are we doing with the extra decades that almost all of us have today, compared to our ancestors of a mere century ago?
Who Wants to Live Forever?
Thought provoking as always!
Thank you for your thoughtful essay!