Evolutionary psychologists argue that selective pressures in our ancestral environment yield a highly specialized set of modular cognitive capacities. However, recent papers in developmental psychology and neuroscience claim that evolutionary accounts of modularity are incompatible with the flexibility and plasticity of the developing brain. Instead, they propose cortical and neuronal brain structures are fixed through interactions with our developmental environment. Buller and Gray Hardcastle contend that evolutionary accounts of cognitive development are unacceptably rigid in light of evidence of cortical plasticity. The developing structure of the brain is both too random and too sensitive to external stimuli to be the product of a fixed genetic mechanism. They also claim that the complexity of the human brain cannot be explained in terms of our meager genetic endowment. There simply are not enough genes to program the intricate neuronal structures that are essential to cognition. I argue that neither of these arguments are persuasive. Small numbers of genes can function to determine diverse phenotypical outcomes through evolutionarily selected developmental systems. Similarly, theories of modularity do not rule out the possibility that innate cognitive systems exploit environmental regularities to guide the developing structure of the brain. Consequently, the anti-adaptionist consequences of these positions should be rejected.