concept

Kerogen

The insoluble organic residue left in sedimentary rock after burial has stripped out everything readily degradable. It is not original material but a transformation product: the starting biomolecules cross-link into a dark, water-repelling, aromatic polymer network that is extremely inert. Wiemann and colleagues showed in 2018 that what had been taken for intact dinosaur protein is in fact this class of polymer. It is why cellular morphology can persist for hundreds of millions of years after the original molecule is long gone.