How on earth didn’t I know about the natural nuclear reaction at Oklo? It’s this sort of enlightened but sadly non-useful trivia that I tend to specialise in. Fascinating stuff, in case you’re worried that this means the world is about to explode, a properly scientific comparison with modern nuclear reactors should set your mind at rest (essentially there just isn’t a high enough percentage of fissile uranium about anywhere anymore to get natural criticality, that’s why you have to enrich the stuff if you want to build a bomb, reactor or just make your hand glow).