The neutral theory in the genomic era

A number of tests have been developed to detect positive selection at the m olecular level. These tests are based on DNA polymorphism within and diverg ence between species. Applications of these tests have revealed a large col lection of genes that have evolved under positive selection and some genera l insights into adaptive evolution. Recently, these tests have been applied on a genomic scale and have provided estimates of the frequency of adaptiv e substitutions and a critical test of the neutral theory.