“Gravity has modeled the evolution of life on Earth, and provides the frame of reference for the body orientation and the integration of accelerations in the various planes of space. Given the importance, ubiquity and stability of the gravitational force during the evolution of life, the organisms have the opportunity to develop without the need to adjust their gravity sensing to the external environment. It seems nevertheless that, in addition to a genetically controlled phase of development for target finding, a stimulus controlled phase is required for the fine tuning of synaptic terminals.”
The auditory and vestibular system share a common origin, with the ear containing the vestibular system first in early vertebrates – the the auditory system emerging from the vestibular system. (De Burlet 1929, Carey and Amin 2006 in Beraneck et al’s chapter in the Development of Auditory and Vestibular Systems edited by Raymond Romand, Isabel Varela-Nieto p451.)
Sensory receptors for both the auditory and vestibular systems are situated within the bony labyrinths of the inner ear. The vestibular system comprises of three semi-circular canals, and the otolith organs; both the utricle and saccule. (Bear et al. 2016)
The vestibular system in co-operation with input from the tactile and proprioceptive systems make it possible for us to move. The contribution of the vestibular system is so significant that when it does not function e.g. in those with vertigo, movement is all but impossible.