The comment of Hankin (2013) elucidated several strengths of the target article (Martel, 2013), in which I reviewed extant literature on sex differences in common childhood-onset externalizing and adolescent-onset internalizing disorders. Hankin also raised important questions about the utility of evolutionary psychological principles, particularly those of sexual selection, to generate novel, specific, and a priori hypotheses about sex differences in common forms of psychopathology. I acknowledge these points, and I contend that a metatheory derived from evolutionary psychological principles is quite useful in 2 ways. First, it provides a parsimonious framework for understanding sex differences across multiple levels of analysis (e.g., hormones, gene by environment interactions, dispositional traits, behavioral and emotional symptoms). Second, it provides a framework for the generation of novel, specific, and a priori hypotheses such as those elucidated in my review. Existing disorder-specific theories cannot do as well in serving these functions. The pursuit of metatheories that both organize existing findings and generate novel cross-disorder hypotheses is crucial for ongoing progress in psychological science. Evolutionary psychology provides one such fruitful metatheory.