Those types of changes are more likely to be seen in regulatory rather than structural genes. The secrets of regulatory genes remain largely unknown...and will likely continue to be for the immediate future. Patience is required, to be sure...but many things have indeed been discovered in the last 50 years.
If my responses seem to cover many different areas it’s because the theory of evolution contains uncertainties in many different ways.
For example, natural selection is logically flawed in that it conflates agency with environment and it contains a consistent ambiguity regarding the problem of survival. That is, for the mouse is the hawk the problem or is the mouse’s fur color the problem? If the fur color is the problem, the agent of solving the problem is the in the mouse’s genes, not in the environment.