Rotting fish experiments reveal how organs fossilise

A photo of a sand-coloured rock plate with the distinctive imprint of a fish fossil at its centre

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Most fossils are bones, but individual organs’ biochemistry determines whether they are preserved in rock

Why certain organs of animals fossilise and others simply disappear has remained a scientific mystery. But researchers in the UK studied the chemistry inside decaying fish while they rotted for two and a half months and discovered that it all depends on each organ’s phosphate levels.