Biological Censor?

I have asked the same sort of question in another thread:Since there is apparently no further argument about microevolution occuring and organisms changing within species (or 'kinds' as they would have it), what is there that places an upper limit on just how different things can get? What sets this 'limit function' to maintain the immutable integrity of a 'kind' and how is the limit determined ?Haven't seen any Creo's bite on that one either.

The issue is dealt with quite well here." ...for biologists, there is no relevant difference between microevolution and macroevolution. Both happen in the same way and for the same reasons, so there is no real reason to differentiate them. ""Creationists act as if there is some magic line between microevolution and macroevolution, but no such line exists as far as science is concerned. Macroevolution is merely the result of a lot of microevolution over a long period of time.""If you find a creationist arguing that microevolution can occur but macroevolution cannot, simply ask them what biological or logical barriers prevent the former from becoming the latter - and listen to the silence."And the silence apparently continues...