Creationism certainly is an essential tenet of Christian fundamentalism. An interesting (and otherwise moving) book to read in this regard is Father and Son by Edmund Gosse. Gosse, an English scholar who later became Librarian of the House of Lords, was born in the C19 into the Plymouth Brethren, of which his parents were among the early saints. His father was a natural scientist of some renown, and spent his life trying to prove scientifically that Darwin, whom he greatly respected, was mistaken. There are still fundies trying to do this, I know one and once knew another.