Despite a decline in sexist language, traditional gender beliefs remain embedded in the scientific literature on reproductive biology and consequently continue to distort knowledge, encumber the learning process, and reinforce gender essentialism. This article analyzes the enduring force of gender stereotypes in Italian middle school science textbooks and a highly popular education film. It identifies a consistent set of stereotypes and assumptions running through textual and visual content regarding fertilization, reproductive anatomy, and human evolution. In addition, the article demonstrates congruence between these materials and students' understandings of fertilization through words and drawings elicited by a worksheet. Findings are examined within the context of pervasive gender stereotypes in textbooks and journal articles on reproductive biology, science and technology textbooks in general, and schoolbooks across subjects. The study shows that assigning gender traits to sex cells, reproductive systems, and ancestral humans misrepresents human biology, endorses a heteronormative vision of femininity and masculinity, and objectifies girls and women. Removing gendered representations from science textbooks is both more challenging and more urgent compared to other textbooks, given that their association with natural truth shields science textbooks from critical scrutiny as well as challenges to conventional conceptual frameworks.