Changes

==Recognition of biotic antecedent==

==Recognition of biotic antecedent==

Extracting high abundances of specific molecular fossils from source rocks dominated by a single type of organism is a reliable means of demonstrating connection.<ref name=ch17r6>Azevedo, D., Aquino Mato, F., Simoneit, B., Pinto, A., 1992, Novel series of tricyclic aromatic terpanes characterized in Tasmanian tasmanite: Organic Geochemistry, v. 18, p. 9–16, DOI: [http://www.sciencedirect.com/science/article/pii/014663809290138N 10.1016/0146-6380(92)90138-N].</ref> A less certain approach, apparently valid in select cases, is based on analogy: we can infer a molecular fossil in a modern organism, identical to a compound from ancient strata, was derived from a closely related ancient organism.

Extracting high abundances of specific molecular fossils from source rocks dominated by a single type of organism is a reliable means of demonstrating connection.<ref name=ch17r6>Azevedo, D., F. Aquino Mato, B. Simoneit, and A. Pinto, 1992, Novel series of tricyclic aromatic terpanes characterized in Tasmanian tasmanite: Organic Geochemistry, v. 18, p. 9–16, DOI: [http://www.sciencedirect.com/science/article/pii/014663809290138N 10.1016/0146-6380(92)90138-N].</ref> A less certain approach, apparently valid in select cases, is based on analogy: we can infer a molecular fossil in a modern organism, identical to a compound from ancient strata, was derived from a closely related ancient organism.

==Limitations==

==Limitations==