Earth has always been a planet of comebacks. Life has thrived, collapsed, and reinvented itself in astonishing ways. Scientists call the five great wipe-outs of the past the “Big Five” – huge mass extinctions that reset the clock on life. Without them, we wouldn’t even be here to talk about it. 

This week, Luke O’Neill dives into what these extinction events can teach us - from the ancient Ordovician seas that suddenly emptied, to the Triassic era where one wave of destruction cleared the stage for the dinosaurs, and the dramatic end of the Cretaceous, when an asteroid put an end to their reign. The most catastrophic of all came at the end of the Permian, nicknamed “the Great Dying,” when nearly everything living was snuffed out. 

What’s extraordinary is the sheer gulf of time between these cataclysms. Tens of millions – even hundreds of millions – of years separated one mass extinction from the next. To put it in perspective, the gap between the end-Triassic and the asteroid strike that finished the dinosaurs is longer than the time between that asteroid strike and today. These are planetary rhythms on a timescale that makes human history look like the blink of an eye. 

But here’s the uncomfortable twist: many scientists now argue that we’re in the early stages of a sixth great extinction. And for the first time, it wouldn’t be volcanoes or asteroids doing the damage – it would be us. Human activity, from climate change to habitat destruction, is putting pressure on life everywhere. 

So what does history tell us? That life will recover. But whether we will be part of that story depends on what we do next. Luke explores how science is helping us understand extinction not as an abstract tragedy, but as a warning sign – and why the choices humans make in the coming decades matter more than ever. 

Send your feedback or ideas for future episodes to Luke at laoneill@tcd.ie.