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Abstract:
Most animals that once lived have gone extinct. The remains of a few of these can be found in museum collections worldwide. As modern evolutionary biology is limited to the use of extant taxa, retrieving DNA from extinct or subfossil organisms can add significant insight into past population history and resolve phylogenies that can be tentative by morphology alone. DNA is a relatively weak molecule, comparatively speaking, yet under certain conditions it persists in the fossil record, despite what in vitro chemistry predicts. While most fossil remains do not contain DNA, museum specimens can be screened for the presence of conditions that would be conducive for nucleic acid preservation by measuring the extent of amino acid racemization and by looking at the extent of protein hydrolysis by pyrolysis gas chromatography/mass spectrometry. Results from these types of analyses suggest that the preservation of DNA is linked to the temperature and its constancy at a site rather than its age. Chemical analyses of coprolites from extinct herbivores from the late Pleistocene, as well as Archaic Native Americans, show the presence of compounds from the Maillard reaction. Upon the cleaving of these products, the defecator can be identified and his diet analyzed.
