How Long Have Humans Got Left? | Unveiled

How Long Have Humans Got Left?

Our planet is an ancient place. And while it can be difficult to comprehend that the Earth had been here for billions of years before we walked out of the sea, it’s also hard to imagine the same expanse of time stretching out ahead of us. Even more challenging is picturing that Earth’s future probably won’t serve to host our particular species.

This is Unveiled, and today we’re answering the extraordinary question; how long have humans got left?

It was Copernicus, the renowned, Renaissance mathematician and astronomer, who first suggested that Earth and the other planets orbit the sun, rather than everything else orbiting the Earth. Over time, it became clear not only that this was true, but that the solar system was not even in the centre of the galaxy, and that our galaxy was just one of innumerable others. This idea that humans are not “privileged observers” – that all of existence doesn’t revolve around us – gave way to the Copernican Principle a few centuries later, arguing that statistically it’s always more likely you’re observing somewhere in the middle of something rather than at the beginning or the end of it. The “something”, in the case of today’s question, is the lifespan of humanity. So, what does that mean for all of us?

The Copernican Principle was perhaps most famously applied by academic J. Richard Gott in 1969 to the Berlin Wall. Since it had been built in 1961, people speculated over how long it would remain. Gott did some sums using the Wall’s known beginning and unknown end… and estimated that there was a 50% chance that it would come down at some point between 1971 and 1993. In 1989, when the Berlin Wall was pulled down, Gott was proven right.

Apply the same concept to the whole of human history then - that we’re not witnessing humanity at its birth nor its death right at this moment - and while results do vary, we can say that our species will die out at some point between 5,100 years and 7.8 million years in the future. Neither of those figures is very large in the grand scheme of the universe, but even the lesser prediction of five millennia gives us at least a little bit of breathing room!

To look at it another way, though, average mammalian species are thought to live between one million and ten million years in total before going extinct naturally. And while the starting point for modern humans is also up for debate, if we say that we’ve already been around for 200,000 years, we have a fairly comfortable minimum of 800,000 years left – a figure that’s again in line with Gott’s predictions. Considering also that the average individual human lifespan is eighty years, we’re talking hundreds of generations before humans go extinct.

But there’s now growing concern that the once “typical” numbers no longer tell the whole story. Lots of other species are actually dying off much faster than they should be; with species disappearing worldwide at up to one thousand times the natural rate, according to the Center for Biological Diversity… As a result the fate of humanity has also grown increasingly uncertain.

Climate change is arguably the biggest threat we face today, and it’s largely brought on by human activity. Again, the numbers tend to fluctuate, but one popular climate change statistic says we only have until 2030 to seriously cut down our CO2 emissions, or else risk the beginning of the end for life as we know it. Before his death, the physicist Stephen Hawking also lowered his prediction for humanity’s longevity from one thousand years to a measly one hundred. And, while it’s not widely expected that the human race will just die out overnight, there are growing numbers who question whether we can make it into the next century unless significant changes are made.

It’s known that a global increase of just a few degrees Celsius can have catastrophic effects, with various predictions covering the total loss of the ice caps, mass flooding across the map, dramatic changes in weather and whole regions of the world one day reaching temperatures that are literally un-survivable. But, even then, some argue that the ever-worsening climate crisis might not actually cause total human extinction. It could - and if the worst fears of climatologists are realised, will - cause thousands of people to die in widespread natural disasters and climate-led apocalyptic situations… but the human race still might find ways to survive (just in much smaller numbers).

There are even more effective and completely inescapable ways that we could meet our end, however. For example, it’s inevitable that one day - in around five billion years - the sun is going to expand into a red giant that will very possibly engulf the Earth in flames. If humans haven’t made it off of this planet by then - or even by roughly one-to-two billion years from now when the sun becomes far too hot on its way to transforming into a red giant - then that’s how long we’ve got left. So, we have the sun’s death to count down to if nothing else! But of course, there are other threats hiding in the solar system that could affect us before then, as well. Another asteroid strike, like the one that wiped out the dinosaurs, could one day spell the end for humans too; or should Earth ever (for any reason) find its orbit or rotation in any way altered, then that could also signal our demise. When it comes to the forces of space and nature, there’s sometimes little that anyone can do!

It’s perhaps natural then that humans have been theorising about our own Armageddon for about as long as we’ve been around. Traditionally, religious texts and teachings have featured various violent cataclysms, while today it feels like conspiracy theories about the “end of days” are everywhere… whether it’s the Millennium Bug, the end of the Mayan Calendar in 2012, or even the Nibiru impact, where it’s said that a rogue planet will one day crash into Earth and destroy it.

There are some more viable threats closer to home, too, like the Yellowstone Supervolcano which, were it to erupt as it’s reportedly scheduled to, would leave us all to choke under a volcanic winter. Humans in the past have also been threatened with widespread contagions like the Black Death or Smallpox, and the so-called “Disease X” - an unknown and potentially untreatable pathogen - looms large and ominous over the future of medicine. In fact, antimicrobial resistance today ranks as one of the World Health Organization’s leading threats to life.

All of which means that predicting our own downfall has become something of an obsession for humans in recent years. So much so that we actually do have a “Doomsday Clock”, a symbolic attempt to measure how close we are to our own extinction. Launched in 1947, the Doomsday Clock has been 2 minutes away from midnight since January 2018 and has never been more than 17 minutes away – which was back in 1991. Maintained by the Bulletin of the Atomic Scientists, its purpose was originally to measure how close we were to an all-out nuclear war… which is yet another unpredictable situation that contributors say could severely shorten our time in this world. Nowadays, though, the Doomsday Clock is about more than only our global arsenal of nuclear weapons; it serves as a constant reminder of the many things that could wipe out humanity.

For hundreds of thousands of years, human life has grown and evolved into what we are today. We’re an intelligent species, yes; We’re reasonably skilled; and we’re able to in some way control a lot (but not all) of what life throws at us. But even we, as with everything else, have a beginning and an end. We weren’t always like we are now, and perhaps one day in the future we will have adapted into some other type of life form entirely - one that can withstand the likes of climate change, asteroid strikes and volcanic ash clouds. Perhaps to our distant descendants, humans will actually rank as quite simple and straightforward beings. But, for now, there are plenty of ways in which we could perish; whether any of them transpire or not, is another question.

It’s impossible to know for certain when humans will have disappeared entirely, but we have a lot of estimates to work with. If we survive to see the sun start to die, then perhaps we’ve got another billion years left in us. But if, before then, we succumb to a world-ending catastrophe of some sort, then our final days could be much closer. If the higher end of the Copernican Principle calculations ring true, we have millions of years in front of us; if it’s the lower end, it’s thousands; but if modern threats like climate change, nuclear war and antimicrobial resistance aren’t addressed, then we could have only a few centuries. And that’s how long humans have left.