Radio carbon dating stone
Scientists now have accurate methods (see below ) for dating fossils.
methods rely on characteristic faunal and geological patterns to bracket the period when the fossil existed.
Very simply, there are five basic principles to this theory:  Variation has a genetic origin (i.e.
is heritable) and arises through processes such as mutation and recombination.
Archaeological geology as a science had to precede the proposal of evolution, as an understanding of the immense age of the earth is necessary to understand evolution.
Mass extinction events and an organism's unique adaptations mark the history of evolution, both of which may lead to adaptive radiation.
 Natural selection, gene flow and random genetic drift (the random change in gene combinations with each generation) drive evolution, resulting in a change in gene frequencies within populations .
 Adaptation is genetically based and so leads to phenotypic changes that accumulate over time;  Speciation (species formation) evolves through reproductive isolation and (genetic) divergence of populations;  Genetic changes through natural selection lead to new species and eventually new taxa .
sapiens (including Neanderthals and Cro-Magnon) (see the modern taxonomic classification of humans).
This formed the foundation of the neo-Darwinian evolutionary theory.
Between the mid-1930s and mid 1940s geneticists, systematists and palaeontologists collaborated to create a united approach to evolution, the "Modern Synthesis".