 Until August 2008, Claassen was the Science editor at the Afrikaans daily paper "Die Burger", published in Cape Town, where he wrote a weekly column on science, "Wetenskap vandag" (Science Today).His review of Leon Rousseau's "Die Groot Avontuur" (The Big Adventure), a book on evolution, sparked an intense debate in Afrikaans newspapers for his criticism of the eminent evolutionary scientist, Prof. Phillip Tobias, for writing an "Avant Propos" for Rousseau's book.Claassen's main criticism of the book was that it supported the idea of evolution by Intelligent Design.