Curriculum statements and textbooks are considered to be vital support tools for teachers, particularly during times of curriculum innovation. A recent change in South Africa was the controversial inclusion of evolution in the school curriculum, raising serious concerns amongst biology teachers regarding the adequacy of their content and pedagogical content knowledge for teaching the topic. Widespread "misconceptions" about evolution make teaching this topic difficult for biology teachers worldwide. Identifying the sources of errors is an essential step needed before addressing them. This study explored curriculum support materials as a possible source of misconceptions, using content analysis of the South African school Natural Sciences curriculum statement and six Grade 7-9 Natural Sciences textbooks from two different publishers, and investigated "curriculum slippages" between the "formal" and "perceived" curricula. The aim was to determine the nature and extent of unscientific ideas about evolution, and to see how authors dealt with potential misconceptions. Errors were found in the curriculum statement and in the textbooks, where they escalated in frequency. Latent problems associated with ambiguous wording of statements posed further problems. Although this paper uses evolution as an example, lessons learned about curriculum materials as a possible influence on misconceptions are applicable to other subjects.