Are Skrulls capable of evolution?

It has been noted on several occasions in the marvel universe that skrulls are "Genetically Frozen in place" an are thus incapable of evolution. But this has been contradicted by numerous. the Skrulls were shown to have a mutant gene. and the superhero group Cadre K consists entirely of mutant Skrulls. And as of the events of "the secret invasion" it has been shown that the new super skrulls are the result of genetic engineering an not the old Bionic process used to create the original super skrull. If they are not capable of genetic change then how is this possible?