Major transformations in the chewing biomechanics of earliest mammals and their influence on the evolution of mammalian hearing

The origin of mammals is a major transition in vertebrate evolution. This transition is accompanied by fundamental transformations of features for feeding (such as jaw and teeth), and sensory function (such as sensitive hearing of high-frequency sound), among a whole suite of evolutionary innovations. During the early mammalian evolution, mandibular bones with both feeding and hearing functions in the earliest mammals separated from the jaw to become the true mammalian middle ear bones specialized only for hearing. Decoupling of chewing mechanism and hearing function is a crucial step in mammalian evolution to be able to increase both the chewing efficiency (food break down in short time) and the hearing ability (reception of higher frequencies). The incorporation of multiple bony elements into the middle ear increased the hearing sensitivity of mammals, most notably to high-frequency sounds, a trait that is thought to have benefited the mammalian lineage.