Why do some Republicans think that liberalism is linked with teaching the theory of evolution?

Republicans are mostly christian. To those folks being anti evolution is a very core issue. They run for office in many cases in order to control what kids are taught in public schools. They fight for God to be taught in the clroom. They call it creationism. Even republicans know that if you call it what it really is, religion, then by law you couldn't teach it in public schools.