Darwin famously wrote “If it could be demonstrated that any complex organ existed, which could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely break down.” This risky prediction generated two different sorts of debate: the first among biologists of the late nineteenth and early twentieth centuries who debated whether Darwin’s claim was correct – must evolution be gradual? – and the other from present-day creationists who argue that certain complex traits refute Darwin’s claim. Yet a partial solution to both was already hinted at by Darwin: organismal bodies are flexible. Phenotypes can change under different environmental stimuli, and this can happen rapidly, dramatically, and in a coordinated fashion. Dr. Morris will introduce the concept of phenotypic plasticity, the capacity of a single genotype to produce multiple environmentally determined phenotypes, and suggest that some modern critiques of Darwin can be put to rest through an understanding of what Darwin called that “most perplexing subject.”