Why do genes have introns? Recombination might add a new piece to the puzzle

Much progress has been made recently regarding when and how spliceosomal introns invaded eukaryotic genomes. Although the 'intron early-intron late' debate seems to be settled, the original and essential question remains: why have introns at all-do they have a purpose? Analyses of the relationship between intron length and recombination in Drosophila shed new light on the forces that drive the evolution of introns. Comeron and Kreitman proposed recently that introns are advantageous because they enhance within-gene recombination and therefore increase selection efficacy (Hill-Robertson effects). However, their observations can also be explained by alternative neutralist models.