PUTTING DATES TO THE PAST: Introduction to the subject. How did we find out the Earth's age History: Scientists who played a role and their contributions (Archbishop Ussher/Lecrerc/Lord Kelvin/Arthur Holmes/Willard Libby) Relative dating methods (stratography). The 4 main Eras (Precambrian, Palaeozoic, Mesozoic and Cenozoic) Fossils. Absolute Dating Techniques. Dendrochronology. Radioactive Absolute Dating. Carbon-14. Laetoli. Our first predecessor to walk upright.