TThe nature of science in genetics education: a historical analysis of Japanese high school biology textbooks, 1963–2023

Background: While international research has explored the Nature of Science (NOS) in textbooks, few studies have systematically analyzed its historical evolution within a specific subject area. Purpose: This study investigates how NOS is represented in the genetics content of Japanese high school biology textbooks from 1963 to 2023. Method: Using the ten-dimensional NOS framework by Abd-El-Khalick et al. (2017), we analyzed 14 textbooks published over the six-decade period. Results: The representation of NOS followed a trajectory of initial growth, a sharp decline in the 1980s under the ‘Relaxed Education’ policy, and a recovery from the 1990s onward. Explicit-reflective (86%–95%) and content-embedded (79%–88%) approaches were predominant. The depth of genetics mechanisms evolved from simple definitions (e.g. mutation) to system-based explanations (e.g. DNA sequence changes and natural selection), emphasizing the Tentative, Theory-laden, and Inferential NOS dimensions. Additionally, portrayals of genetic discoveries shifted from linear narratives to multidimensional, socially embedded perspectives. Conclusions: Historical curriculum reforms and advances in scientific knowledge jointly shaped the presentation of NOS in Japanese genetics education. These findings offer valuable insights for future curriculum design and NOS-integrated science education globally.