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Seventy thousand years ago, a supervolcanic eruption may have driven humanity to the brink of extinction. Long before that, a big asteroid wiped out the dinosaurs — and last week, a little asteroid reminded us that we’re not invulnerable to that either.
As scientists have learned more about space, they’ve discovered more unlikely-but-not-impossible ways that the cosmos could wipe us out — from gamma ray bursts, poorly understood astronomical events that release lots of energy, to nearby stars going supernova (none of them look likely to do so soon).
All of that might make you wonder: What are the odds that natural (as opposed to man-made) risks will drive humanity extinct? A new paper published Tuesday in Scientific Reports, by Andrew E. Snyder-Beattie and Michael Bonsall of Oxford’s Mathematical Ecology Research Group and Toby Ord of Oxford’s Future of Humanity Institute, tries to answer that question with a clever new approach. While other researchers have tried to describe different natural events that might pose an extinction risk, this paper looks at the problem from another angle.
There’s one obvious way to estimate the odds that the natural world will wipe us out: count up all the ways it could possibly do that, from supervolcanos to gamma ray bursts, and check how likely it is that at least one of those will happen. But, the authors point out, there’s a serious problem with that approach.
“A lot of the risks that are on this list are ideas that were discovered pretty recently,” Ord told me. A few decades ago, we didn’t know about gamma ray bursts or a terrifying type of volcanic eruption called a flood basalt, where a high volume of lava covers a large share of the planet’s surface area. Now, both are on the list. In a few decades, there could be more things on the list.
Doesn’t that make it impossible to confidently estimate the odds that nature will drive us extinct? After all, maybe there’s a big threat we’ll learn about in the coming years.
The paper argues that, actually, it doesn’t make estimating our overall risk impossible. It just suggests we need a different approach. With one simple assumption — that certain categories of risks to humanity have not increased over the thousands of years since early humans walked the Earth — it’s possible to estimate the aggregate likelihood that any of those risks will drive us extinct even if we don’t know what each of those risks are.
Here’s the argument: If you’ve done something a hundred times before without a problem, and nothing has changed, the odds that it’ll go badly this time are pretty small, right? If you’ve done it 20,000 times, they’re even smaller.
Estimates of how long anatomically modern humans have been around vary, but it’s likely at least 200,000 years. That means humanity has done this “existing without getting wiped out, for a year” thing 200,000 times before.
That gives us an upper bound on how likely all of the natural hazards in the world are to kill us, combined: They have to be unlikely enough that they haven’t struck in any of the past 200,000 years. That means, the paper argues, “we can be exceptionally confident” that our chances of being driven extinct by natural phenomena are less than one in 14,000 each year.
If we start counting not just from the emergence of anatomically modern humans but from the first instances of the genus homo — which includes modern humans as well as Homo erectus and Homo neanderthalensis — then we’ve been around a lot longer, and we could estimate that our chances of being driven extinct are less than one in 140,000 a year.
Extinction risks from nature might be small. But other extinction risks loom large.
Ninety-nine percent of all the species that have ever lived on Earth have gone extinct. Humans might go extinct too, and we don’t take the possibility as seriously as would perhaps be wise. The emerging technologies that threaten the future of human life on Earth are largely understudied, and certainly underdiscussed in policy — they likely won’t be mentioned in the Democratic primary debates, for example.
Ord, Bonsall, and Snyder-Beattie’s analysis suggests that natural risks, at least, remain deeply unlikely. Of course, this only estimates the odds of being driven extinct by phenomena whose threat hasn’t changed (or has decreased) over the past 200,000 years. “200,000 years of track record of not going extinct from nuclear war doesn’t count for much,” Ord pointed out, “since we only invented nuclear weapons 70 years ago.” It doesn’t account for risks from anthropogenic global warming, either, and it’s not clear whether the risks from pandemics have been decreasing or increasing.
But there’s value just in quantifying the risks from natural causes, even though this still leaves us with lots of risks to address. A clear picture of which threats to humanity are most plausible can help us prioritize our efforts to reduce existential risks — and can be an effective reminder that our fate is mostly in our own hands.
The paper is “an argument that we’re very unlikely to go extinct from the kind of natural causes that we’ve been vulnerable to for the whole of humanity’s life,” Ord told me.
As for whether we’ll go extinct from everything else? That’s up to us.
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