Chemical preservation of plants and insects in natural resins

The morphological preservation of fossils in amber is remarkable, but their chemical composition is largely unknown. The likelihood of DNA preservation in amber has been questioned but, surprisingly, the fate of more decay–resistant macromolecules such as ligno–cellulose in plants or the chitin–protein complex in insect cuticle has not been investigated. Here we report the results of investigations using pyrolysis–gas chromatography/mass spectrometry (py–GC/MS) of the tissues of insects and the plant Hymenaea from ancient and sub–fossil resins (2–20 ka) from Kenya, and from Dominican amber (25–30 Ma). The volatile components of the resin have penetrated even the internal tissues, resulting in the exceptional three–dimensional preservation of amber inclusions. Chitin is preserved in the bee and ligno–cellulose in the Hymenaea leaf from the Kenyan resins. There was no trace, however, of these macromolecules in tissues in Dominican amber. The presence of aliphatic polymer and sulphur–containing moieties in these tissues indicates that they have undergone diagenetic alteration; in view of this, the preservation in Dominican amber of a macromolecule as labile as DNA would be extraordinary.