RACE TO THE TOP. “If Y-linked genes are incessantly evolving to improve male function and compete with other male genotypes, the changes may drive the evolution of recombination suppression, and thus recombination modifiers may also spread, some of which may themselves be on the Y (for instance, inversions).”
http://www.nature.com/hdy/journal/v95/n2/full/6800697a.html