Crossing over is thought to be evolutionarily advantageous because it continually shuffles genetic alleles into novel combinations. until recently, it was thought that the genes on the y chromosome might degenerate because they lack homologous genes on the x chromosome with which to pair up prior to crossing over. however, when the y chromosome was sequenced, eight large regions were found to be internally homologous to each other, and quite a few of the 78 genes represent duplicates. (y chromosome researcher david page has called it a “hall of mirrors.”) explain what might be a benefit of these regions.