Just looking at a few proteins on RCSB PDB lets us all know that for sure, unequivocally, without question, nature is great at copy – paste – mirror – rotate.  It is apparently an easy way to achieve variation. 1, 2, 3, 4, 5 and 6 (i am sure there are jillions more, i just stopped at 6). Great for defining new functions and structure-function relationships while conserving effort allowing for flexibility in evolution