The modern theory of Evolution adds the idea and concept of population genetics, developmental biology and paleontology. Presently evolution is explained as the change of gene frequencies in gene pool that takes place in many years. In this process, natural selection favors some individuals with mutations. These individuals then contribute larger portion of their gene combination to the gene pool. Therefore modern theory of evolution by natural selection explains change in allele frequencies in a gene pool that is also caused by the process of migration, gene flow and chromosomal variations.