Numerous sex differences in obsessive-compulsive disorder (OCD) instantiations are likely universal, as the associated evolutionary threats and concerns onto which they map were differentially important to the two sexes. Hence, although some ritualized behaviors or thoughts are indeed culture-specific, others are both culturally and temporally invariant as they are rooted in universal Darwinian etiologies (e.g., the sex differences in OCD symptomatology posited here).