Excerpts from an article written by Max Roser (March 15, 2022, "our World in Data Org")
If we manage to avoid a large catastrophe, we are living at the early beginnings of human history
The point of this text is not to predict how many people will ever live.
What I learned from writing this post is that our future is potentially very, very big. This is what I try to convey here.
If we keep each other safe – and protect ourselves from the risks that nature and we ourselves pose – we are only at the beginning of human history.
Our past
Before we look ahead, let’s look back. How many came before us? How many humans have ever lived?
It is not possible to answer this question precisely, but demographers Toshiko Kaneda and Carl Haub have tackled the question using the historical knowledge that we do have.
There isn’t a particular moment in which humanity came into existence, as the transition from species to species is gradual. But if one wants to count all humans one has to make a decision about when the first humans lived. The two demographers used 200,000 years before today as this cutoff.
The demographers estimate that in these 200,000 years about 109 billion people have lived and died. It is these 109 billion people we have to thank for the civilization that we live in. The languages we speak, the food we cook, the music we enjoy, the tools we use – what we know we learned from them. The houses we live in, the infrastructure we rely on, the grand achievements of architecture – much of what we see around us was built by them.
Our present
In 2022 7.95 billion of us are alive. Taken together with those who have died, about 117 billion humans have been born since the dawn of modern humankind.
This means that those of us who are alive now represent about 6.8% of all people who ever lived.
These numbers are hard to grasp. I tried to bring it into a visualization to put them into perspective.
It’s a giant hourglass. But instead of measuring the passage of time, it measures the passage of people.
Each grain of sand here represents 10 million people: each year 140 million babies are born. So we add 14 grains of sand to the hourglass. Every year, 60 million people die; this means 6 grains pass through the hourglass and are added to the large number of people who have died.
Our potential future
How many people will be born in the future?
We don’t know.
But we know one thing: The future is immense, the universe will exist for trillions of years.
We can use this fact to get a sense of how many descendants we might have in that vast future ahead.
The number of future people depends on the size of the population at any point in time and how long each of them will live. But the most important factor will be how long humanity will exist.
Before we look at a range of very different potential futures, let’s start with a simple baseline. We are mammals. One way to think about how long we might survive is to ask how long other mammals survive. It turns out that the lifespan of a typical mammalian species is about 1 million years.
Let’s think about a future in which humanity exists for 1 million years: 200,000 years are already behind us, so there would be 800,000 years still ahead.
Let’s consider a scenario in which the population stabilizes at 11 billion people (based on the UN projections for the end of this century) and in which the average life length rises to 88 years.
In such a future, there would be 100 trillion people alive over the next 800,000 years.
The chart visualizes this. Each triangle represents 7.95 billion people – it is the green triangle shape from the hourglass above and corresponds to the number of us alive today.
Each row represents the birth of half a trillion children. For 100 trillion births there are 200 rows.
If you disagree with the numbers I use in my scenario it is easy for you to see how different numbers would lead to different futures. Here are two examples:
If you think the world population will stabilize at a level that’s 50% higher than in my calculation, then the number of future births will be 50% higher. The chart would be 50% wider. It would show the births of 150 trillion children.
If you think the world population will have a size of just one billion people, then the chart would be only an eleventh as wide and would show 9.1 trillion births.7
One thing that sets us apart is that we now – and this is a recent development – have the power to destroy ourselves. Since the development of nuclear weapons, it is in our power to kill all of us who are alive and cause the end of human history.
But we are also different from all other animals in that we have the possibility to protect ourselves, even against the most extreme risks. The poor dinosaurs had no defense against the asteroid that wiped them out. We do. We already have effective and well-funded asteroid-monitoring systems and, in case it becomes necessary, we might be able to deploy technology that protects us from an incoming asteroid. The development of powerful technology gives us the chance to survive for much longer than a typical mammalian species.
Our planet might remain habitable for roughly a billion years. If we survive as long as the Earth stays habitable, and based on the scenario above, this would be a future in which 125 quadrillion children will be born. A quadrillion is a 1 followed by 15 zeros: 1,000,000,000,000,000.
A billion years is a thousand times longer than the million years depicted in this chart. Even very slow moving changes will entirely transform our planet over such a long stretch of time: a billion years is a timespan in which the world will go through several supercontinent cycles – the world’s continents will collide and drift apart repeatedly; new mountain ranges will form and then erode, the oceans we are familiar with will disappear and new ones open up.
But if we protect ourselves well and find homes beyond Earth, the future could be much larger still.
The sun will exist for another 5 billion years. If we stay alive for all this time, and based on the scenario above, this would be a future in which 625 quadrillion children will be born.
How can we imagine a number as large as 625 quadrillion? We can get back to our sand metaphor from the first chart.
We can imagine today’s world population as a patch of sand on a beach. It’s a tiny patch of sand that barely qualifies as a beach, just large enough for a single person to sit down. One square meter.
If the current world population were represented by a tiny beach of one square meter, then 625 quadrillion people would make up a beach that is 17 meters wide and 4600 kilometers long. A beach that stretches all across the USA, from the Atlantic to the Pacific coast.
And humans could survive for even longer. What this future might look like is hard to imagine. Just as it was hard to imagine, even recently, what today might look like. “This present moment used to be the unimaginable future,” as Stewart Brand put it.