In the last decade or so, creationism has grown sophisticated. Oh, the old-fashioned creationists are still around, especially in the Bible Belt. They're the ones who believe that the earth is only a few thousand years old, that God created it and all its inhabitants in six days and that fossils are a product of Noah's flood. In the early 1990's, however, a new breed of creationists appeared. These ''neo-creos,'' as they have been called, are no Dogpatch hayseeds. They have Ph.D.'s and occupy positions at some of the better universities. The case they make against Darwinism does not rest on the authority of Scripture; rather, it proceeds from premises that are scientific and philosophical, invoking esoteric ideas in molecular biology, information theory and the logic of hypothesis testing.