paleobiochemistry

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The study of chemical processes used by organisms that lived in the geological past. Most information on the nature of life in the geological past comes from the study of fossils; a record of biochemical processes that occurred can be found in the organic molecules of sedimentary rocks and fossils. The organic matter in fossil fuel deposits and finely dispersed in shales and limestones represents the debris of cells which have been chemically altered to a more stable form. A comparison of the molecular structure of these preserved organic compounds with that of components of living cells enables the researcher to identify similarities and dissimilarities between past and present biochemistry.

Paleobiochemical studies have shown that a number of the common chemical processes used by living organisms today have been in use for a very great length of time. Paleobiochemical techniques are also used on materials returned from extraterrestrial sources to determine whether life exists outside of Earth. See also Paleoecology; Paleontology.