Like unhappy families, all mass extinctions are unhappy in their own way. But their aftermaths are surprisingly similar. It takes millions of years, but life eventually bounces back
In the 1980s, as the Alvarez hypothesis gained ground, it seemed reasonable to assume that all mass extinctions were caused by impacts. Though there have been numerous "discoveries" of craters and other impact signatures coinciding with the other mass extinctions, none has stood up to scrutiny. It now seems that the KT event was unique - the only mass extinction caused by an impact. In fact, we now think that each mass extinction had its own unique cause.
Another idea that was fashionable in the 1980s was that mass extinctions are periodic. Some palaeontologists claimed to have found patterns in the fossil record showing a mass extinction every 26 million years, and they explained this by suggesting that a "death star", dubbed ...
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