Chapter 2 examines the evolution of the stomatognathic system in mammals, highlighting how the advent of mastication marked a turning point in craniofacial anatomy. The emergence of chewing triggered a profound structural reorganization involving teeth, muscles, jawbones, joints, and soft tissues. The shape and number of teeth, dental roots, and the development of heterodonty are presented as functional responses to specific biomechanical demands. The chapter also explores the role of masticatory and facial muscles (lips and cheeks), emphasizing their importance not only in chewing but also in regulating occlusion and enabling social communication. Special attention is given to the functional anatomy of the tongue and its coordination with other elements of the oropharyngeal system. Additionally, it delves into how bone tissue responds to mechanical stimuli, showing how chewing influences the modeling and remodeling of the skull. The skull is described as a dynamic structure composed of interconnected bony units joined by sutures capable of dissipating forces, with a focus on the relationship between muscle development and skeletal adaptations. Overall, the chapter illustrates how the masticatory function has been a key factor in shaping the evolution and organization of the mammalian stomatognathic system, deeply interwoven with posture, encephalization, and cranio-cervico-mandibular dynamics.