 Species who have gene clusters have a selective evolutionary advantage because natural selection must keep the genes together.Over a short span of time, the new genetic information exhibited by the duplicated copy of the essential gene would not serve a practical advantage; however, over a long, evolutionary time period, the genetic information in the duplicated copy may undergo additional and drastic mutations in which the proteins of the duplicated gene served a different role than those of the original essential gene.Over the long, evolutionary time period, the two similar genes would diverge so the proteins of each gene were unique in their functions.