If modern human civilisation collapsed — as a result of nuclear war, severe climate change, or a much worse pandemic than COVID-19 — billions of people might die.

That's terrible enough to contemplate. But what’s the probability that rather than recover, the survivors would falter and humanity would actually disappear for good?

It's an obvious enough question, but very few people have spent serious time looking into it -- possibly because it cuts across history, economics, and biology, among many other fields. There's no Disaster Apocalypse Studies department at any university, and governments have little incentive to plan for a future in which their country probably no longer even exists.

The person who may have spent the most time looking at this specific question is Luisa Rodriguez — who has conducted research at Rethink Priorities, Oxford University's Future of Humanity Institute, the Forethought Foundation, and now here, at 80,000 Hours.

Links to learn more, summary and full transcript.

She wrote a series of articles earnestly trying to foresee how likely humanity would be to recover and build back after a full-on civilisational collapse.

There are a couple of main stories people put forward for how a catastrophe like this would kill every single human on Earth — but Luisa doesn’t buy them.

Story 1: Nuclear war has led to nuclear winter. There's a 10-year period during which a lot of the world is really inhospitable to agriculture. The survivors just aren't able to figure out how to feed themselves in the time period, so everyone dies of starvation or cold.

Why Luisa doesn’t buy it:

Catastrophes will almost inevitably be non-uniform in their effects. If 80,000 people survive, they’re not all going to be in the same city — it would look more like groups of 5,000 in a bunch of different places.

People in some places will starve, but those in other places, such as New Zealand, will be able to fish, eat seaweed, grow potatoes, and find other sources of calories.

It’d be an incredibly unlucky coincidence if the survivors of a nuclear war -- likely spread out all over the world -- happened to all be affected by natural disasters or were all prohibitively far away from areas suitable for agriculture (which aren’t the same areas you’d expect to be attacked in a nuclear war).

Story 2: The catastrophe leads to hoarding and violence, and in addition to people being directly killed by the conflict, it distracts everyone so much from the key challenge of reestablishing agriculture that they simply fail. By the time they come to their senses, it’s too late -- they’ve used up too much of the resources they’d need to get agriculture going again.

Why Luisa doesn’t buy it:

We‘ve had lots of resource scarcity throughout history, and while we’ve seen examples of conflict petering out because basic needs aren’t being met, we’ve never seen the reverse.

And again, even if this happens in some places -- even if some groups fought each other until they literally ended up starving to death — it would be completely bizarre for it to happen to every group in the world. You just need one group of around 300 people to survive for them to be able to rebuild the species.

In this wide-ranging and free-flowing conversation, Luisa and Rob also cover:

• What the world might actually look like after one of these catastrophes
• The most valuable knowledge for survivors
• How fast populations could rebound
• ‘Boom and bust’ climate change scenarios
• And much more

Get this episode by subscribing to our podcast on the world’s most pressing problems and how to solve them: type 80,000 Hours into your podcasting app.


Producer: Keiran Harris
Audio mastering: Ben Cordell
Transcriptions: Katy Moore