Ear development, like all other sensory systems, evolved from smaller structures in smaller animals. Research based on the work of Andrea Streit, however, places the burden of ear development solely on vertebrates (1H). Marine vertebrates developed the first set of mechanoreceptors that could be classified as sound detectors since sound waves and pressure waves are almost the same form of energy. Once animals evolved to the stage where it was possible to cross land, the receptors were no longer able to perform the same tasks they once performed underwater, leading to the beginning of the development of the ear as the we know today. The transition from a fluid environment to an air environment triggered the development/strengthening of the middle ear and the external collecting apparatus. In a marine environment, water can carry sound very far and efficiently. In the air, sound disperses and rapidly loses its energy, requiring a large pickup apparatus, the external ear. Internally the middle ear was a response to convert the sound energy of the air into an input that could be appropriately scaled and transferred to the fluid medium of the inner ear (2H). Primitive land animals still retained the structures of their marine counterparts and as such did not. have more modern facilities specifically adapted for aerial hearing; a closed middle ear cavity and the tympanic membrane (1H). The bones of the middle ear were also not developed to the level seen in later vertebrates, the main difference being the stapes. In humans it is one of the 3 ossicles of the middle ear that transfer mechanical energy to the fluid of the inner ear. In early terrestrial vertebrates it was integrated into the brain case and served as a secondary support structure. See Figure 1H for a normal… half of the paper… lia, a clotting factor VII deficiency, a targeted drug can possibly alter that gene and institute partial function and creation of the deficient protein. discussed earlier in this article, human genes for hearing and amphibian genes for hearing are remarkably similar, and that similarity would only become closer as one moves forward in the phylogenetic map, as shown in Figure 3H and Figure 4H. The implications of this, at the human level, are that drug trials can be performed using many animals and will still be relevant to the development of the human ear. The most expensive phase of any therapeutic trial is the human clinical trial due to the extreme length of time required and the manpower needed to coordinate the trial. If this could be shortened through the use of viable animal models, testing for relevant genes, then drug costs could conceivably fall dramatically.