Why do you ask? Is that the only thing holding you back from accepting the theory of evolution? Would evidence of that change your mind?
Scientific theories are supposed to be based on empirical observation. If evolution is true such mutations should be happening all over the place. So if there's a lack of such, it should be seen as significant.
Is that the only thing holding you back from accepting the theory of evolution? Would evidence of that change your mind?
I would say that would be one major hurdle. There's still others, such as the mathematical likelihood of each and every such mutation building on the last one and being passed on to successive generations without the particular variation dying etc. So no, not by itself. I'm only asking about micro-evolution, not macro.