The human race’s prospects of survival were considerably better when we were defenceless against tigers than they are today, when we have become defenceless against ourselves.—Arnold Toynbee (1)
The human race probably faces a greater risk of extinction today than at any time in recorded history. The eminent cosmologist Martin Rees has put the human race’s chances of surviving this century at just 50%. (2) Nick Bostrom has found that academic risk experts generally give us an 80-90% chance of survival, which is better but hardly reassuring. (3) Before the development of modern technology, we faced a relatively low level of what Bostrom calls “existential risk.” But while our mastery of technology has increased our ability to protect ourselves against environmental dangers, it has also made us a much greater threat to our own survival. Now we have reached a critical phase in our development as a species: if we don’t learn to manage our growing technical power, we are in danger of destroying ourselves. (4)
Genetic evidence suggests that the human race came close to extinction at least once in its history. We remain vulnerable to the same planetary disasters that have threatened life on Earth before. A gamma-ray burst in the vicinity of our solar system, like the one that some think triggered the Ordovician extinction 450 million years ago, would threaten life on Earth by destroying the planet’s ozone layer. Another asteroid like the one that caused the extinction of the dinosaurs 65 million years ago would probably also threaten the survival of the human race. Or a volcanic eruption the size of the one that occurred in Sumatra around 73,000 years ago—which may have been what pushed the human race to the brink of extinction—would probably put the human race in similar danger again. But while a natural disaster on a planetary scale is always a possibility, such disasters seem to be relatively rare.
The greater danger to the survival of the human race comes not from nature but from human beings. Although technology has given us the ability to avoid certain kinds of catastrophe, it has also given us the ability to cause disasters on a planetary scale. In fact, the worst catastrophes of the last century were not natural disasters—not earthquakes, tsunamis, or volcanic eruptions—but wars and political atrocities. One reasonable estimate is that 180 million people died in some type of mass political violence in the 20th century, which makes it in absolute terms by far the bloodiest century in human history. That death toll was made possible by advances in the technology of killing. The enormous explosive power of nuclear weapons in particular raised the real possibility that we could wipe out the entire human race and drastically alter the atmosphere of the planet in a single military conflict. And the technology of killing continues to advance.
Even technologies that were not designed for killing pose a threat to our survival. Our incredible capacity as a species to control our environment entails an incredible capacity to destroy our environment. Increasingly, new technologies like genetic engineering put the power to destroy in the hands of individuals or small groups. Moreover, as we have moved into cities and away from the production of basic necessities, we have become dependent as a species on a global economy to provide those necessities. If that system breaks down, billions of people will be unable to secure food and water. As it becomes cheaper and easier to cause widespread destruction—whether deliberately or by mistake—the greater the chance of catastrophe becomes.
At the same time, technology magnifies our collective impact on the planet. We have already dramatically altered the conditions of life on Earth in ways that we never intended. We have hunted many species to extinction. We are driving others extinct by disrupting their habitats faster than they can adapt, so that we are now in the middle of a planetary extinction event largely of our own making. The International Union for Conservation of Nature estimated in 2010 that nearly one-fifth of vertebrate species are currently threatened. While the number of human beings is not for the moment declining—in fact our growing numbers contribute to the extinction of other species—we may ultimately be disrupting our own habitat faster than we will be able to adapt.
Climate change is just one aspect of the problem, but NASA climatologist James Hansen warns that it already constitutes a “planetary emergency.” Global emissions of CO2 were at record levels in 2011. In fact, evidence from ice cores suggests that the level of atmospheric CO2 is now higher than it has been at any other time in at least the last 800,000 years. As Bill McKibben points out, energy producers already have more than 5 times as much fossil fuel in development as climate scientists generally think it would be safe to burn. (5) As it was, last year was the hottest year on record in the continental U.S., with temperatures averaging 1.8 °C (3.2 °F) above the 20th-century average. And January 7 of this year was the hottest single day in Australian history, with temperatures across the country averaging over 40 °C (105 °F). If the melting arctic permafrost releases its huge stores of methane into the atmosphere, the result could be runaway planetary warming.
Every generation seems to imagine the world is about to end. There is something self-centered about believing we happen to live at the final moment of human history. In the end, our millenarian fantasies mostly seem—like the supposed Mayan apocalypse—pretty silly. With our ability to adapt to changing circumstances, we have been fairly resilient as a species. Nevertheless, as Jared Diamond has argued, there’s reason to believe that human societies have destroyed themselves in the past. (6)
We can’t take too much comfort in the fact that we’ve survived as a species for as long as we have. After all, no living species has a history of going extinct. Moreover, when we look at our own history, we’re not looking at a data point chosen at random from the histories of all intelligent species. The fact that we are even around to look at our own history means that we at least avoided extinction. But because having survived this long is a requirement for even being to consider the question, it isn’t evidence that intelligent species in general are able to avoid extinction. Indeed, the fact that we have yet to find evidence of intelligent life elsewhere in the galaxy should worry us. Peter Ward and Donald Brownlee may be right that—in spite of evidence that there may be 10 billion earth-like planets in the galaxy—the conditions for intelligent life to develop in the first place are very rare. (7) Otherwise it may be that intelligent life is relatively common, but rarely survives the critical stage when it develops technology capable of bringing about its own destruction.
In the end, this is a political problem: for the human race to flourish, we will have to work together as a species to use our technology and our resources wisely. Our environmental and resource problems would be largely manageable if we collaborated to find solutions. And if we did a better job of managing political conflict—and spent less time actually preparing to kill one another—our collective chances of survival would certainly improve.
But that will be a challenge. In 1955, the philosopher Bertrand Russell released a public letter—which became known as “The Russell-Einstein Manifesto” after Albert Einstein added his signature a few days before his death—warning of the dangers of nuclear war. In the letter, Russell called on people to put aside their feelings about politics and consider themselves “only as members of a biological species which has had a remarkable history, and whose disappearance none of us can desire.” (8) Russell and Einstein were right that just about no one—unfortunately, not absolutely no one—wants to see the end of the world. Nevertheless, the Russell-Einstein Manifesto was naive to suggest political conflict would disappear if we recognized our common interests. It’s not just that we have to take more seriously a danger we would rather ignore. Political conflict arises not just because people are short-sighted or selfish, but also because well-meaning people can reasonably disagree about what to do and who should bear the costs of action. In fact, cooperation is sometimes harder to achieve when more is on the line. In this case, our very future is at stake.
We have overcome unprecedented obstacles before. We should not be pessimistic about what we can do. Erle Ellis has rightly pointed out that human beings have a history of “transgressing natural limits and thriving.” (9) But nor should we be blindly optimistic about our prospects. Even a small chance of catastrophe should be unacceptable—and failing to take the danger seriously could doom us. The truth is that now more than ever we have the power to determine our fate as a species. “We are as gods,” Stewart Brand has written. “We have to get good at it.” (10)
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