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Big bangs and mega-deaths
Have you heard about mass extinctions? Probably not...
Have you heard about mass extinctions? Probably not... but because of people doing so much damage to the planet and to the web of life, lots of animals and plants are dying out completely. That's what extinction is. And once a creature is extinct, that's it. There are no second chances. It's gone for ever.
But there's nothing new about mass extinctions. Ninety nine percent of all the different types of life - called species - which have ever lived are now extinct. What is completely new is that this is the first extinction caused by people and their wasteful and polluting ways. All the other extinctions in Earth's long history seem to have been caused by violent natural events.
The best known of these was the final extinction of the dinosaurs about 66 million years ago.
Less well-known but much worse was a mysterious mega-extinction that happened about 250 million years ago. This was so bad that it destroyed around 96% (96 out of every hundred) of all species of life on the planet.
Understanding mass extinction shows that the global life system is delicate. If it's messed up, it could mean the complete collapse of the life-support systems we all depend upon.
The important lesson to learn from mass extinctions is that they hit complex life hardest. It's things like bacteria and rats and cockroaches that survive -- not people or (sob!) penguins. You have been warned!