Dog skull shape challenges assumptions of performance specialization from selective breeding

Through selective breeding, humans have driven exceptional morphological diversity in domestic dogs, creating more than 200 recognized breeds developed for specialized functional tasks such as herding, protection, and hunting. Here, we use three-dimensional reconstructions of dog skulls to ask whether these function-oriented kennel-club groups reflect differences in morphology that correspond to those functions. We analyzed 117 canid skulls, representing 40 domestic dog breeds and 18 wild subspecies, using geometric morphometric techniques and k-means clustering. Results show near-full overlap in kennel-club groups and with natural species, except for companion dogs having extreme snout shape. When categorized by task-specific historic function (i.e., bite work and scent work), this morphology overlap remains. These results indicate that, despite producing extreme morphological diversity, humans have not produced breeds specialized for functional tasks.