A paper that appeared in Scientific Reports by Evans et al. (1)asked whether changes in the genotypes of target mosquito populations would occur due to introgression of released transgenic mosquito genomes. The paper in fact describes the introgression of released mosquito strain genome into wild populations of Aedes aegypti after releases of the OX513A strain developed by Oxitec and the paper has generated a lot of controversy. Is this a surprising finding or an entirely predictable outcome? Is it cause for alarm?