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.
There could be different type of scenarios for Human's future,
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.
Scenario 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.
Conclusion
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.
