This is the story, revisited by current eyes and means, of a mathematical biology problem explored in the 1930s in Thomas Morgan’s laboratory, in California. It is one of the early developments of evolutionary genetics and quantitative phylogeny, and deals with the identification and counting of chromosomal rearrangements in Drosophila from comparisons of genetic maps. A re-analysis by present day mathematics and computational technologies of the data produced in the 1930s unveils how the solicitation of a mathematician led the team of biologists, against their first intuition, to an erroneous conclusion about the presence of phylogenetic signal in gene orders. This illustrates the role of errors in scientific activities, as well as some unexpected difficulties of multi-disciplinary collaborations. Also underlying is the possible influence of computational complexity in understanding the directions of research in biology.