Geologic Time Scale
Geologic Time Scale: Its History and Development
Scottish geologist James Hutton (1726-1797) set the stage for the development of the geologic time scale in the late 18th century with the publication of his Theory of the Earth (1785). In it, Hutton advanced "uniformitarianism," a geological doctrine which basically assumes that current geologic processes, occurring at the same rates observed today, in the same manner, account for all of Earth's geological features, a principle later championed by British geologist Sir Charles Lyell (1797-1875). Next, British civil engineer, surveyor and amateur geologist William Smith (1769-1839) made the discovery that fossils are found buried in a definite order. The geologic time scale was developed shortly thereafter.
Geologic Time Scale: What Is It?
What is the geologic time scale and how does it work? Well, the earth's crust consists of many layers of sedimentary rock (called "strata"). Geologists assume that each layer represents a long period of time, typically millions of years. This is actually a secondary assumption based upon the primary assumption of Uniformitarianism. These layers of sedimentary rock contain billions of fossil remains and some of these fossils are unique to certain layers. The layers are catalogued and arbitrarily arranged into a specific order (not necessarily the order in which they are found). This order reflects the assumption of macro-evolution (the widely held notion that all life is related and has descended from a common ancestor). The creatures thought to have evolved first are considered to be the oldest and are thus placed at the bottom of the column of layers. The creatures thought to have evolved later are higher up and so on. This has led many competent, accredited scientists to object, as this poses a circular argument: how can evolution be the basis for geologic conclusions while geology is taught as the basic evidence for evolution? "Are the authorities maintaining on the one hand, that evolution is documented by geology and, on the other hand, that geology is documented by evolution? Isn't this a circular argument?" (Larry Azar, "Biologists, Help!" Bioscience, vol. 28, November 1978, p. 714).
A variety of fossils from each layer of strata have been chosen to be what are called "index fossils". Index fossils are how we date the sedimentary rock layers. Paleontologists assume the age of an index fossil by the stage of evolutionary history the fossil is assumed to be in. They guess how long it would take for one kind of life to evolve into another kind of life and then date the fossils and rocks accordingly. Once again, this is a circular argument. "And this poses something of a problem: If we date the rocks by the fossils, how can we then turn around and talk about the patterns of evolutionary change through time in the fossil record?" (Niles Eldridge, Time Frames, 1985, p. 52)
Geologic Time Scale: Circular Reasoning
The geologic time scale employs yet another circular argument. We determine the age of the rock by the assumed age of the index fossils it contains, then, to determine the age of all the other fossils in the same layer of rock, we look at the age of the layer of rock in which they are found. "…Geologists are here arguing in a circle. The succession of organisms has been determined by a study of their remains embedded in the rocks, and the relative ages of the rocks are determined by the remains of organisms that they contain." (R. H. Rastall, "Geology", Encyclopedia Britannica, vol. 10, 1954, p. 168)
"In about 1830, Charles Lyell, Paul Deshayes, and Heinrich George Bronn independently developed a biostratigraphic technique for dating Cenozoic deposits [the geologic time scale]…. Strangely, little effort has been made to test this assumption. This failure leaves the method vulnerable to circularity." (Steven A. Stanley, Warron O. Addicott, and Kiyotaka Chizei, "Lyellian Curves in Paleontology: Possibilities and Limitations", Geology vol. 8, September 1980, p. 422)
"The intelligent layman has long suspected circular reasoning in the use of rocks to date fossils and fossils to date rocks. The geologist has never bothered to think of a good reply, feeling that explanations are not worth the trouble as long as the work brings results. This is supposed to be hard-headed pragmatism." (J. E. O'Rourke, "Pragmatism Versus Materialism in Stratigraphy", American Journal of Science, vol. 276, January 1976, p. 47)
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