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Fossil

Collier's New Encyclopedia (1921)

originally, "all bodies whatever that are dug out of the earth are by naturalists commonly called by the general name of At present, any body, or the traces of the existence of any body, body, whether animal been or vegetable, which has buried in the earth by natural causes; one of the bodies called organic remains. Even the cast of a fossil shell, that is the impression which it has left on the rock, is deemed a fossil. (Used often in the plural.) In the early part of the 16th century fossils were supposed by some Italians have been formed in the hills by the FOSSIL SKELETON OF HYRACOTHERIUM VENTICOLUM, FROM EOCENE STRATA action of the stars, a view which, prior to 1579, Leonardo da Vinci combatted. Then the hypothesis arose of a plastic force, or, according to Andrea Mattioli, a fatty matter capable of fashioning stones into organic forms. But the hypothesis which held its place longer than any other, and is not yet extinct among the unscientific, is that they were relics of the Mosaic deluge. It is now thoroughly proved that the relics are really those plants and a animals, that they were nearly all of them in existence ages before the Mosaic deluge, that they are not nearly contemporaneous with each other, but differ in age by untold millions of years, that there is at least a progression among them, if not even the evolution of the last from the more antique. There are breaks or gaps in the series of fossiliferous strata, especially one between the Paleozoic and the Secondary strata, and another between the Secondary and the Tertiary. Mr. Darwin showed that it is almost exclusively strata desposited in seas or lakes which at the time were slowly sinking that have been preserved; those formed when land was rising have as a rule, been washed away. In the older strata, and sometimes in those not so ancient, fossils have been destroyed by metamorphic action, and when any rock is called non-fossiliferous or azoic, the cautious geologist means by the term only that fossils have not been found in it up to the present time.

What Has Changed in the Last Century

Collier's in 1921 could only say that fossils "differ in age by untold millions of years" and that rocks called azoic merely lacked fossils so far. Radiometric dating, developed through the twentieth century, replaced that vagueness with figures: the Earth is about 4.54 billion years old, and stromatolites and microbial traces push the fossil record back some 3.5 billion years, so the Precambrian is no longer blank. The gaps the entry noted have also been filled and explained — the Ediacaran organisms recognised from the 1940s and 1950s, the reinterpretation of the Burgess Shale animals from the 1970s, and the 1980 Alvarez impact hypothesis for the extinction at the end of the Cretaceous. Even the specimen in the caption has moved: the little Eocene horse long labelled Hyracotherium in North America has since been reassigned, with Eohippus and related names restored for the American species.

Written for this edition, 2026.