The ratio of human X chromosome to autosome diversity is positively correlated with genetic distance from genes

The ratio of X-linked to autosomal diversity was estimated from an analysis of six human genome sequences and found to deviate from the expected value of 0.75. However, the direction of this deviation depends on whether a particular sequence is close to or far from the nearest gene. This pattern may be explained by stronger locally acting selection on X-linked genes compared with autosomal genes, combined with larger effective population sizes for females than for males.