Acknowledgements Introduction his document discusses the way radiometric dating and stratigraphic principles are used to establish the conventional geological time scale. It is not about the theory behind radiometric dating methods, it is about their application, and it therefore assumes the reader has some familiarity with the technique already refer to "Other Sources" for more information. As an example of how they are used, radiometric dates from geologically simple, fossiliferous Cretaceous rocks in western North America are compared to the geological time scale. To get to that point, there is also a historical discussion and description of non-radiometric dating methods. A common form of criticism is to cite geologically complicated situations where the application of radiometric dating is very challenging.
Human Evolution Timeline Interactive | The Smithsonian Institution's Human Origins Program
A theory of changes in organic design through controlled random mutations and contingent selection Francis Steen, revised 25 March The Neo-Darwinian Synthesis In broad terms, contemporary evolutionary theory builds on the synthesis of Darwin's ideas of natural variation and selection and Mendel's model of genetic inheritance accomplished by R. Haldane, and Sewall Wright in The Unit of Selection. The central realization of the neo-Darwinian synthesis is that natural selection is best understood to be acting on variation among elements that persist.
Human Evolution Timeline Interactive
Evolution of nervous systems Scientists can infer that the first brain structure appeared at least million years ago, with fossil brain tissue present in sites of exceptional preservation. A long term human study comparing the human brain to the primitive brain found that the modern human brain contains the primitive hindbrain region — what most neuroscientists call the protoreptilian brain. The purpose of this part of the brain is to sustain fundamental homeostatic functions.
Each of these kinds was created with a vast amount of information. There was enough variety in the information in the original creatures so their descendants could adapt to a wide variety of environments. All sexually reproducing organisms contain their genetic information in paired form. Each offspring inherits half its genetic information from its mother, and half from its father.