This paper presents a conservative statistical test to evaluate the neutral theory of molecular evolution, which predicts that regions of the genome evolving at high rates will also exhibit high levels of polymorphism within species. The test is based on a constant-rate neutral model and requires data from interspecific comparisons and intraspecific polymorphism levels in the same regions. The test statistic, \(X^2\), measures the deviation of observed from expected values and is used to assess the fit of the neutral model. The test is applied to data from the Adh locus and its 5' flanking sequence in Drosophila melanogaster and Drosophila sechellia, where the data deviate from the model, suggesting the presence of balanced polymorphism in the coding region. The authors discuss the limitations of the test, including the assumption of no recombination within loci and the impact of linkage between loci, and conclude that the test is sensitive to departures from the neutral model, particularly in the coding region.This paper presents a conservative statistical test to evaluate the neutral theory of molecular evolution, which predicts that regions of the genome evolving at high rates will also exhibit high levels of polymorphism within species. The test is based on a constant-rate neutral model and requires data from interspecific comparisons and intraspecific polymorphism levels in the same regions. The test statistic, \(X^2\), measures the deviation of observed from expected values and is used to assess the fit of the neutral model. The test is applied to data from the Adh locus and its 5' flanking sequence in Drosophila melanogaster and Drosophila sechellia, where the data deviate from the model, suggesting the presence of balanced polymorphism in the coding region. The authors discuss the limitations of the test, including the assumption of no recombination within loci and the impact of linkage between loci, and conclude that the test is sensitive to departures from the neutral model, particularly in the coding region.