Waddington used the concept of canalisation to explain his experiments on genetic assimilation. In these experiments, he exposed Drosophila pupae to heat shock. This environmental disturbance caused some flies to develop a
crossveinless phenotype. He then selected for crossveinless. Eventually, the crossveinless phenotype appeared even without heat shock. Through this process of genetic assimilation, an environmentally induced phenotype had become inherited. Waddington explained this as the formation of a new canal in the epigenetic landscape.
It is, however, possible to explain genetic assimilation using only quantitative genetics and a threshold model, with no reference to the concept of canalisation. However, theoretical models that incorporate a complex
genotype–phenotype map have found evidence for the evolution of phenotypic robustness contributing to genetic assimilation, even when selection is only for developmental stability and not for a particular phenotype, and so the quantitative genetics models do not apply. These studies suggest that the canalisation heuristic may still be useful, beyond the more simple concept of robustness.