Mendel at the sesquicentennial of ‘Versuche über Pflanzen-Hybriden’ (1865): The root of the biggest legend in the history of science

•The idea that Mendel was the first geneticist is still widespread.•It is nourished by ontological intuitions: innate cognitive biases.•It is also and foremost underpinned by a conceptual void in the historiography of biology.•This void concerns the paradigm-shift that facilitated the birth of transmission genetics.•Mendel's thought about the transmission of traits was determined by the old paradigm.

In 1965, Mendel was still celebrated as the undisputed founder of genetics. In the ensuing 50 years, scholars questioned and undermined this traditional interpretation of his experiments with hybrid plants, without, however, managing to replace it: at the sesquicentennial of the presentation of his ‘Versuche’ (1865), the Moravian friar remains, to a vast majority, the heroic Father of genetics or at least some kind of geneticist. This exceptionally inert myth is nourished by ontological intuitions but can only continue to flourish, thanks to a long-standing conceptual void in the historiography of biology. It is merely a symptom of this more fundamental problem.‘Historians of science are trained and paid to replace simple stories (…).’1M.J.S. Hodge