Unable to edit my prior comment, but found research that appears to dispute your claim; citing notable research might help me better understand your claim.

It is very possible that I'm missing something, but that's not how evolution works to my knowledge, adoption of substantially new genetic features is rapid, but refinements or removal of unrelated genetic code is slow if it is not impacted by the substantive mutations.

For more information, see "Long-term phenotypic evolution of bacteria":

http://www.columbia.edu/~gap2118/papers/nature13827.pdf