As the body decomposes the fluids are slightly acidic. Because they had nowhere to drain, they had reacted with the wood of the inner coffin to form a weak humic acid, which strips the bonds between the base pairs (the building blocks of the DNA double helix) and the helical backbone. So the genomic information had dissolved into a thick, black soupy deposit at the bottom of the coffins, resembling a rich chocolate mousse (anatomists are prone to using food analogies to describe substances they encounter – not terribly appropriate, perhaps, but effective).
