The Last Human – A Glimpse Into The Far Future
Because of the potential size of the future, the most important thing about our actions today might be their impact on future generations. This simple-sounding idea has some surprising moral implications
The future of humanity seems insecure. Rapid climate change, political division,
our greed, and failings make it hard to look at our species with a lot of optimism and so many
people think our end is in sight. But humans have always thought they lived in the end times. Every
generation assumes they’re important enough to witness the apocalypse and then life just goes on.
This is a problem because it leads to short-term thinking
and prevents us from creating the best world for ourselves and our descendants. What makes
this worse is that we may actually BE living at an extremely critical moment in human history.
To understand why, let us look at the temporal window of humanity and ask:
When will the last human be born and how many people will there ever be?
These sorts of estimates come with a lot of uncertainties, so please take
them with a gigantic grain of salt. To get a sense of how many people there will be,
let us see how many have already lived. Modern humans arose some 200 thousand years ago.
They were uniquely good at making tools, telling stories,
thinking abstractly, planning and working together in large groups beyond their close family.
Still there were not that many of us. Surpluses in food were sparse, survival was hard,
life expectancy was low. It took us 150,000 years to grow to a population of 2 million.
Improvements were gradual and eventually led to the agricultural revolution,
arguably the biggest change in our history. This was when our numbers really started
growing. It took ten thousand more years to get to 300 million. But that increase was dwarfed
by the industrial revolution. In 1800 there were a billion of us. The human population
doubled in just 120 years and then again in fifty. Today, we number around 8 billion.
In total, over the last two hundred thousand years about 117 billion humans were born and lived,
and 109 billion also died. Which means that about 7% of all humans that ever lived are alive
right now. As many as were born in the first 150,000 years of human history. Every minute,
270 babies join the party. But there are not just more people, never before have we been as healthy
and well off, or lived longer. With growing living standards our birth rates collapsed.
The UN estimates that around the year 2100 we will hit our population peak and there
will be 125 million people born each year. It is pretty unlikely that birth rates will
stay stable forever, but let’s pretend to make our thought experiment simpler.
How many people there will be in the future depends on when our species will die out.
And here we find a lot of uncertainties. We are able to destroy ourselves through
our own inventions – but we are also able to find solutions to avert catastrophic risk.
We can change the direction of planet killer asteroids but we’ve also invented nuclear weapons.
We discovered antibiotics but also carry diseases across the globe in a matter of days. Our
industrial system gave us an incredible standard of living but also changed the atmosphere in the
process. It is very hard to say if human ingenuity will prolong or shorten our species’ lifespan.
If things go badly our end could come suddenly. But if we manage to avoid that,
we could conceivably stick around for a long time. So every day we don’t destroy ourselves
may mean life for an unfathomable number of humans. How many people are we talking about?
It depends on how far our species is going to expand.
Scenario 1: Humans will never leave Earth
If we stay on our home planet, a good metric to look at is the extinction rate of animals
that we get from the fossil record. The average lifespan of mammalian species is
in the region of 1 million years, with some surviving up to 10 million years.
Our close relative homo erectus survived for about 1.9 million years.
Let us be conservative and assume that humans will survive for a million years, which leaves
us 800,000 more years to dawdle away. Assuming a stable birth rate of 125 million people each year,
this means there are roughly 100 TRILLION humans waiting to be born.
850 times greater than the number of people that have ever lived.
This would make everybody alive today only 0.008% of all people that will ever live.
Think about where this leaves you. Instead of putting you at the end of the chaotic
mess that was our past, it would mean you live at the very beginning of something big.
The start of the human story rather than the end. Doesn’t this feel incredibly different?
And now consider that this may be an extremely pessimistic estimate.
If we match the survival time of the most successful mammals, then our future numbers
rise to 1.2 quadrillion people that have yet to be born. And even this seems far from our potential:
As the sun slowly gets hotter and brighter, earth will remain habitable for about 500 million years,
giving so many more potential people the chance to become actual people.
And now let’s begin to think big.
Scenario 2: Humans will leave Earth
We went from humans worshipping the moon, to humans walking on it,
so who knows how much farther we can go? If we don’t die out within the next few hundred years,
ideas that seem outlandish right now become serious considerations.
If we believe that we have a chance of surviving for maybe millions of years,
then we could expand onto the other planets or into our own artificial worlds. Life needs
three things: a surface, resources and energy.
Our Sun provides energy for billions of years and there is so much water and material floating in
the asteroid and kuiper belt that we could sustain many times our current population.
Instead of living on planets, we could decide to construct our own artificial worlds and habitats.
With resources and energy so abundant, we could try out different types of society and ways of
life. An interconnected civilization spanning the solar system would create the basis of existence
for an absurd number of individuals, orders of magnitude more than if we stick to earth, even
if it only existed for a few million years. This future doesn’t have to be grim and dark as science
fiction likes to paint it. With quadrillions of people waiting to be born, we will have billions
of doctors working on curing cancer, billions of problem solvers working on ending poverty and
billions of video game developers making life fun. More humans may actually mean more progress.
Another upside of leaving earth and spreading out is that it becomes much harder for us to
become extinct, as you need a solar system wide catastrophe to catch everybody.
So aside from nearby supernovae or Gamma Rays bursts,
humanity would be relatively safe from extinction, maybe for billions of years.
If we manage to survive for that long, slow evolution or genetic engineering might split us
into multiple species, or we might intentionally keep ourselves the same as we are now.
So to account for that, we’ll just talk about people from now on, instead of humans.
Ok. Now let us think really big.
Szenario 3: People leave the Solar System
As enormous as the solar system is, it is just one star system among billions in the milky way.
If future people can colonize, say, 100 billion stars and live there for 10 billion years, while
each generating 100 million births per year, then we can expect something like a hundred Octillion
lives to be lived in the future. This is a 1 with 29 zeros, a hundred thousand trillion, trillion.
We can spin this up as much as we like. The Andromeda Galaxy will merge with the Milky way,
adding another trillion stars for us to settle. Red Dwarfs stay active for up to a trillion
years and future civilizations might even find energy for their habitats around black holes.
A sufficiently advanced civilization of our descendants might even try to reach other
galaxy groups. While these numbers are mind blowing, they may underestimate the number of
unborn people by many orders of magnitude. If we divide the total energy available in a galaxy by
the average energy needs of a single person, then we get a tredecillion potential lives.
A million, trillion, trillion, trillion potential people.
Hopefully what has become evident is that if we don’t kill ourselves in the next
few centuries or millennia, almost all humans that will ever exist, will live in the future.
Which brings us back to us, in the present. We exist at a highpoint of human history,
with incredible possibilities at our grasp. Technological, environmental and societal.
What we do matters for all the people who do not exist yet.
So while it is not en vogue to think about humanity’s long term future with
optimism – or to think about it at all –, maybe this has given you a bit of perspective.
If we screw up the present, so many people may never come to exist.
Quadrillions of unborn humans are at our mercy. Even if we go with fairly conservative estimates,
the unborn are by far the largest group of people – and the most disenfranchised. Somebody who might
be born in a thousand or even a million years deeply depends on us today for their existence.
This is why it is important to think about the distant future and why our presence is so crucial,
why it matters what we do today. One day the last human will be born. We don’t know when.
But if we change our perspective from us living at the end of the human story,
to us living at the very beginning we can not only build a wonderful world for us
and for them but also for countless numbers of others.
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