FOR PALAEONTOLOGISTS, fossils are buried treasure, and, like treasure of the more conventional sort, such finds are not all of equal value. Fossilised bones, while useful, are reasonably common. Preserved impressions in fine sediment of soft parts like skin and organs are rarer and concomitantly more helpful when it comes to understanding what ancient life was like. But the palaeontological equivalent of finding royal jewels is the discovery of soft tissues that have themselves become preserved. Until now it has been assumed that soft-tissue preservation is a chance, and therefore unpredictable, event. But work published in Geology by Farid Saleh of Claude Bernard University in Lyon, France, suggests that regular variations in Earth's orbit can affect the preservation of soft tissue in predictable ways.
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