Tuesday, July 15, 2014

What is a fossil?

Fossil = the remains or traces of an ancient organism preserved by natural processes in the Earth.  

[Note: the word fossil is derived from Latin, "fossilis," meaning dug up].

The definition of a fossil seems straightforward, but its component parts need some explanation.

remains = hard-body parts like shell, bone, teeth, wood, leaves, pollen; as well as soft-body parts like skin, hair, toenails, organs.

traces = indications of the behavioral activities of an organism (e.g., footprints, dwelling burrows, feeding trails, tracks, boreholes, tooth marks, arrowheads, pottery). Trace fossils are called  ichnofossils; in my last blog I mentioned that ichnology is the study of trace fossils.

ancient = must be older than 10,000 years (older than the Holocene). This age is admittedly arbitrary but it was picked by an international council because 10,000 years is beyond recorded history.

Question: Is a 2,000-year-old Egyptian mummy a fossil?
The answer is no: because it is too young, and it was preserved via a technique used by humans (this technique of mummification is not considered to be a "natural" process).

natural (i.e., non-human-related) processes: fossils are preserved by 1) burial in ice, amber (tree sap), asphalt, dry caves; 2) burial in sediment and later converted into hard rock via compaction and cementation; 3) imprints consisting of only carbonized residue of the organism (insects, leaves, and fish are commonly preserved in this manner).

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