Evolution of the cochlea Evolution of the cochlea Cochlea is Latin for “snail, shell or screw” and originates from the Greek word κοχλίας "kohlias". The modern definition, the auditory portion of the inner ear, originated in the late 17th century. Within the mammalian cochlea exists the organ of Corti, which contains hair cells that are responsible for translating the vibrations it receives from surrounding fluid-filled ducts into electrical impulses that are sent to the brain to process sound. This spiral-shaped cochlea is estimated to have originated during the early Cretaceous Period, around 120 million years ago. Further, the auditory innervation of the spiral-shaped cochlea
Evolution of the cochlea motor function in land vertebrates, but this developed vastly differently in different lineages. In certain birds and mammals, prestins function as both transporters and motors, but the strongest evolution to robust motor dynamics only evolved in therian mammals. It is hypothesized that this motor system is significant to the therian cochlea at high frequencies because of the distinctive cellular and bony composition of the organ of Corti that allows the prestins to intensify movements of the whole structure. Modern ultra-sound echolocating species such as bats and toothed whales show highly evolved prestins, and these prestins show identical sequence alterations over