This article explores the trajectory of the global controversy over the introgression (or not) of transgenes from genetically modified maize into Mexican indigenous maize landraces. While a plurality of knowledge-making processes were deployed to render transgenes visible or invisible, we analyze how a particular in-vitro based DNA-centred knowledge came to marginalize other forms of knowledge, thus obscuring other bio-cultural dimensions key to the understanding of gene flow and of maize diversity. We show that dominant molecular norms of proof and standards of detection, which co-developed with the world of industrial monocropping and gene patenting, discarded and externalized non-compliant actors (i.e. complex maize genomes, human dimensions of gene flow). Operating in the name of high-science, they hence obscured the complex biological and cultural processes that maintain crop diversity and enacted a cultural-political domination over the world of Mexican landraces and indigenous communities.