The negative English morphene, un- and its equivalents, was not born naturally; it was invented, like all languages, out of the need to easily reverse word meanings from positive to negative. There is no question as to the early need for the negative, as shown by the Sanskrit an-. In dozens of words since, the un- has proved its utility many times over; for sure, the un- is in.
"Dial N for Negative,"
Word Ways: Vol. 20
, Article 14.
Available at: http://digitalcommons.butler.edu/wordways/vol20/iss4/14