Why do animals go extinct? You asked Google – here’s the answer

A man pulls from his pocket a futuristic, streamlined flat metallic box that has been constructed in China but filled with chemical components dug from great underground mines in what was once a vast, unspoilt South American wilderness. Looking through a glass screen, forged with heat produced from the burning of 400m-year-old fossil swampbeds, the man considers the question he would like to type into his metal box, a request that would involve it interacting remotely with an air-conditioned server room in a data centre in coastal Finland. He types the question “Why do animals go extinct?” and there is a silent pause before the universe shatters with irony into a million pieces.

It’s easy to point the finger at humans when talking about the global extinction crisis. But the first thing to say about extinctions is that they are not new and they aren’t always our fault. When one looks at the great chapters of life written within layers of strata, for instance, one sees extinction is rather a common phenomenon in the history of life on Earth. In fact, of all of the species preserved as fossils, 99.9% belong to extinct groups. That means, to a close approximation, that all life is extinct, as Prof Norman MacLeod at London’s Natural History Museum puts it.

So why is extinction so common? Bluntly, species are replaced. They are outcompeted by new arrivals: squashed out by new species built by an unthinking agent we call natural selection. Individual by individual, we imagine, species may have been starved out by competitors, or roughed up by storms, droughts, floods, novel diseases, parasites or, perhaps most often, a combination of all of these things. Many species will last 5m or 6m years, however, so they are hardly a flash in the pan, but their inevitable decline will nearly always arrive. Everything alive is in the grip of extinction. It is just a matter of degree.

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