Carbon dating is a technique used to determine the approximate age of once-living materials. It is based on the decay rate of the radioactive carbon isotope 14 C, a form of carbon taken in by all living organisms while they are alive. Before the twentieth century, determining the age of ancient fossils or artifacts was considered the job of paleontologists or paleontologists, not nuclear physicists. By comparing the placement of objects with the age of the rock and silt layers in which they were found, scientists could usually make a general estimate of their age.
Plato (427—347 B.C.E.)
Plato | Internet Encyclopedia of Philosophy
Before the 20th cent. Estimates of the absolute age of prehistoric and geological events and remains amounted to little more than inspired guesswork, as there was no scientific basis for testing such proposals. However, as the basic principles of relative dating progressed during the course of the 19th cent. Stratigraphic dating is accomplished by interpreting the significance of geological or archaeological strata, or layers.
The discovery of the radioactive properties of uranium in by Henri Becquerel subsequently revolutionized the way scientists measured the age of artifacts and supported the theory that Earth was considerably older than what some scientists believed. However, one of the most widely used and accepted method is radioactive dating. All radioactive dating is based on the fact that a radioactive substance, through its characteristic disintegration, eventually transmutes into a stable nuclide.
Racial mixing has always taken place in regions where various racial groups have been in contact with one another. The scale of such crossing grew considerably after the great geographical discoveries of the 15th to 17th centuries and the subsequent colonial expansion and slave trading. It is a natural phenomenon in human history and proves the untenability of the reactionary theory of polygenism the theory of the origin of the principal races of mankind from different ancestors, thereby ascribing Caucasoids, Mongoloids, and Negroids to separate species.