INTRONS AND THE KEY TO EVOLUTION. “Spliceosomal introns might well be one of the genomic feature that eukaryotes must put up with because of small population sizes. When these genic interruptions (found in all eukaryotes but, as yet, not in prokaryotes) were first discovered, Gilbert ventured that their presence held the key to the enhanced evolutionary potential of eukaryotes.”
http://www.pnas.org/content/112/33/10278.full